beginning versioning stuff - incomplete
refactoring...
Warn on non-yaml files
Added new-style test files (not valid yet)
Added atfile processing
model load working, atfile fix
minor
used each_with_index
add functions mocked up
Updated currency_group files
Improvements

Options no longer a singleton
Create temporary files for Option tests
Make Ditto::Entity a class
Refactoring
fix simple_object.xml
ongoing...
Stored instance versions
dependency checking almost ok...
Circular dependency checks working
use flat_map to save lines!
Change mappings to use {} not do/end
Store working without version checks...