Made compositional IC plugins ready for being derived from SimulatorAccess.

Removed the geometry_model pointer that was stored as default in interface.cc
Remove an outdated TODO, leave a new one.
Unified the handling of initial conditions to other plugins.

Previously used pointers to geometry_model, adiabatic_conditions and
boundary temperature were removed and replaced by calls to
SimulatorAccess as in all other plugins. This will break user-defined
plugins, which use these pointers.
fix doxygen formatting in header
comment wrapping, doxygen formatting
run astyle
wrap comments again
fix copyright year
Changed an Assert to an AssertThrow.
Merge pull request #86 from gassmoeller/simulator_access_initial_conditions

Simulator access initial conditions
Merge pull request #89 from tjhei/fixes

Code formatting and astyle