Full weaving support

[szschaler]

Will fix #12 .

Currently, a weave clause requires one of the morphisms to be an interface_of morphism. For full support of the theory, we should allow both to be full morphisms.

• [x] Adjust validation to allow such weave clauses
• [x] Clean up composer code separating inner classes into their own proper top level classes to simplify readability.
• [x] Add a test case
• [x] Adapt composition algorithm so that it can support such weave clauses
  • [x] Introduce an explicit notion of a Span between EObjects that can explicitly denote a set of arrows from one object in the kernel GTS to the left and right GTS elements, respectively.
  • [x] Use the set of Span objects instead of the current inverted index to drive the merging of elements.
  • [x] Use three values for originKeys: LEFT, KERNEL, and RIGHT.
  • [x] Keep two sets of unmapped elements, from left and right mapping, respectively.
  • [x] Update naming strategies
  • [x] Make sure all composer tests run again
• [x] Create explicit mappings from interface_of specifications
• [x] Refactor
• [x] Update documentation

[szschaler]

Basic restructuring has been done in a first cut; now need to run tests and debug through them