Removed n_batches from statepoint
Added error for restarts with small n_batches
Add 'implicit none' to modules
Merge branch 'develop' into no_n_batches_in_statepoint

Conflicts:
	docs/source/devguide/statepoint.rst
Merge pull request #334 from smharper/implicits

Add 'implicit none' to modules
Pass argument to fatal_error.
Merge branch 'no_n_batches_in_statepoint' into develop
Fix problem with -t, --track command-line flag.
Added support for plot level depth, removed id from filename
Updated documentation
Fixed plot filename issue
Allow cells with no surfaces.
Updated docs for cells with no surfaces
Fixed typo for #341
Merge pull request #341 from smharper/no_surfaces

Ability to model cells with no surfaces
Merge pull request #340 from nhorelik/plot_level

Support for plotting cells/mats on middle universe levels
Fix typo from last merge.