New Temperature Initialisation scheme

A shell unconstrained in temperature and velocity is used for a natural
evolution of temperatures above the indenter. A second shell with
linear-radial increasing temperatures to 1 set along the bottom ensures
a more reasonable temperature profile along the bottom.
The top surface nodes are fixed in velocity, so that no material from
the surface is subducted, which leads to too low temperatures.

Squashed commit of the following:

commit 9177a243c5439f5cf9fc7bd084efe8fdf121c823
Author: Matthias Schmiddunser <matthias.schmiddunser@uni-tuebingen.de>
Date:   Tue Dec 9 13:30:00 2014 +0100

    Fixing calculation

    Changed the temperature calculation in relax-shell

commit 406363377a64dcae62cb71064f40c88cdd11538d
Author: Matthias Schmiddunser <matthias.schmiddunser@uni-tuebingen.de>
Date:   Mon Dec 8 11:13:45 2014 +0100

    Fixed typo in xshell calculation

    minus sign switched

commit b29f80c745acd2ddd1aba72e84f081e8e3a6b0bb
Author: Matthias Schmiddunser <matthias.schmiddunser@uni-tuebingen.de>
Date:   Fri Dec 5 10:16:46 2014 +0100

    Adding parameter read and updating input file

commit 9ef0d88dcb4e9433d0c84b1aa6c2534d40dfdffc
Author: Matthias Schmiddunser <mschmiddunser@argand.geowissenschaften.uni-tuebingen.de>
Date:   Thu Dec 4 17:55:48 2014 +0100

    Adding a temperature relaxation zone

    Second spherical shell (relaxshell), in which temperatures along bottom
    bi-linearly increase to mimic relaxation

commit f0bbcb0641160e29dae13a7f93c517ddec36e54e
Author: Matthias Schmiddunser <matthias.schmiddunser@uni-tuebingen.de>
Date:   Thu Dec 4 14:12:12 2014 +0100

    Fix bottom temperature in 2 shellwidth distance

    Bottom nodes in twice the shellwidth distance are fixed to temperature 1
    in order to get a smooth tranisition

    Also adjusting the surface fixation.

commit 61cacda33de538ac546b8eee5929734b61b3c018
Merge: 8485230 a1b5f83
Author: Matthias Schmiddunser <matthias.schmiddunser@uni-tuebingen.de>
Date:   Thu Dec 4 11:10:27 2014 +0100

    Fixing Surface nodes for initalisation

    Merge commit 'a1b5f83' into tinit2
    Previously discarded because did not converge, but might have been due to other
    problem. Trying anew.

commit 848523074de2440200558ccdb4500aa8fd32600e
Author: Matthias Schmiddunser <matthias.schmiddunser@uni-tuebingen.de>
Date:   Thu Dec 4 10:26:11 2014 +0100

    Leavig bottom temperature entirely unconstrained

    Temperature gradient along bottom beyond the spherical shell is too
    steep, so trying not to constrain the bottom at all.

commit 71f872b8de52dce10655768750b94312eac4ed06
Merge: a2ab6e6 c8473b72
Author: Matthias Schmiddunser <matthias.schmiddunser@uni-tuebingen.de>
Date:   Thu Dec 4 10:22:18 2014 +0100

    Merge branch 'douarw_rotsub' into tinit

    Conflicts:
    	src/define_bc_rot_sub_init.f90
    	src/read_input_file.f90
    	test/input_schmiddu.txt

commit a1b5f83b5b97e26101b24d317d44dab7957b2334
Author: Matthias Schmiddunser <matthias.schmiddunser@uni-tuebingen.de>
Date:   Mon Dec 1 09:54:43 2014 +0100

    Fixing surface  in spinup

    For wider spherical shells, fix two topmost nodes

commit a2ab6e6b1d55b62c0e83285259b8064cb213f8cd
Author: Matthias Schmiddunser <matthias.schmiddunser@uni-tuebingen.de>
Date:   Thu Nov 27 13:48:05 2014 +0100

    Added input parameter for T=0 elevation

    Using parameters%ztemp creates error, since this value is usually chosen
    to be above uppermost surface.

commit d95ee1204978053b305f577adf9d624a4afb1b97
Author: Matthias Schmiddunser <matthias.schmiddunser@uni-tuebingen.de>
Date:   Tue Nov 25 14:44:32 2014 +0100

    New Temperature Init setup

    Rotating indenter, nonmoving bulk and a spherical shell without
    temperature or velocity constraints in between

commit 1436995156dac0a11afd94abc2c81389a2c13cc3
Author: Matthias Schmiddunser <matthias.schmiddunser@uni-tuebingen.de>
Date:   Fri Nov 21 13:59:26 2014 +0100

    kfixt for part of bottom option

    bottom temperature gets fixed to 1 at the bottm after a belt of
    width fixbelt from the indenter outline

commit 59245b5146df8f97a30b8177f8a4b43b0b6e5b09
Author: Matthias Schmiddunser <matthias.schmiddunser@uni-tuebingen.de>
Date:   Thu Nov 20 15:04:10 2014 +0100

    Extending options for fixed velocity in domain

    domainfix now allows choosing of which section (indenter, rest of
    domain, or both) will be fixed in velocity

commit 3b89c4d8d273269ee5e9eecff4c75288cb523a62
Author: Matthias Schmiddunser <matthias.schmiddunser@uni-tuebingen.de>
Date:   Tue Nov 18 16:18:08 2014 +0100

    Removing basal temperature contraint

    kfixt = 0 for entire base.
    Also adding geotherm for x=1 and fixing temp.