Make TpHandleSet introspectable for g-i

Submitted by Simon McVittie

Assigned to Telepathy bugs list

Link to original bug (#29267)

Description

+++ This bug was initially created as a clone of Bug #29197 +++

I wrote:

If you're going to (skip) methods to avoid having to think about whether/how they should be introspected, we should have a way to keep track of which ones are deliberately (skip)'d, and which ones we just haven't thought about yet. I suggest opening one bug for each class visible to introspection.am that's partly (or not at all) annotated.

For instance, the properties on TpBaseConnection should be pretty uncontroversial.

Version: git master