Fix a bug in the parsing scripts, setting double to int
Work on a generic simulation class
Move LuaMara to modules/unigrid.lua
Merge branch 'gravity'
Update core modules and utils

+ util.plot Gnuplot function accepts dense or sparse tables
+ util.pretty_print understands classes
+ classes understand __call__ metamethod
+ optparse does not demand help options
Begin working with simulation module
In the middle of demonstrating that collapse1d problem works right