Implement automatic construction of restructured text references for data items in the objects file

[bskinn]

Restructured text references should follow a consistent format every time. Therefore, it should be possible to write a generator to produce those references for users to copy and paste into their source.

It seems like this would be particularly useful with #24.

This is actually nontrivial, though, because the role names within the objects.txt data lines aren't identical to the role commands used in the reST. (E.g., it's py:function inside the objects.txt, but :py:func:... in the reST.)

[bskinn]

Need to test whether using the full role name in a reST reference is still recognized by Sphinx.

If so, then this is already implemented by the as_rst property on the DataObjs!

[bskinn]

Nope, you have to use the shorter inline directives for cross-references, not the longer block directives.

[bskinn]

Superseded by #234.