restructure to alchemy package
adding a relationship between object and slice.
WIP adding link point source <-> slice
automatically generating point sources and linking mos point sources upon calculate_slice_geometries.
changes to import statements
finished restructuring to many-to-many relationship
added some documentation for the MOSObjects
moved the documentation into mos. general documentation restructure
Merge pull request #57 from wkerzendorf/gmos/mos/add_mos_object

add MOS Object