Fix a number of linking issues

[agjohnson]

This addresses a number of linking issues, and includes a light refactor of how we are building up the domain data.

This drops the need for accumulating a special dictionary using the format:

(object type, object name) -> (object full name, object role type)

This was originally written this way to combine roles like class and cls into a single lookup. Instead, this improves on the role mapping and doesn't explicitly state the object type. The domain object mapping now uses the common format of:

object_name -> (object full name, object role type)

The only deficiency of this is that when multiple objects have the same name, but different types, the first object will be the one to receive reference links. This shouldn't be an issue for most use cases however.

• Objects are mapped in a standard way
• A global role obj was added, to allow any style references
• New fields were created to reference this object type, for automatic linking. This piece required the obj role above, and is the basis for refactoring the object storage
• References now support ~
• The generated index output was repaired
• Additional object lookup mechanisms were added, for backing down to a wider search breadth

Fixes #48 Fixes #52

[ericholscher]

Are there any tests that should be added that verify this works or enables things to work in a new fashion? Looks sane to be otherwise.

[agjohnson]

The only new functionality is the addition of ~ parsing, though I should be able to add this as a full Sphinx build and testing the output. I'll add that.

[agjohnson]

Added tests for ~ shortening syntax

[ericholscher]

:+1: