efl-mono: Use alternate docs when a property has no doc

efl-mono: Use alternate docs when a property has no doc

Summary:
Use the getter or the setter documentation when a property has no documentation.
This is not ideal (all properties should have documentation!) but at least we
have less undocumented properties.
See for example Efl.Canvas.Vg.Above.

Test Plan:
The Efl.Canvas.Vg.Above property in src/lib/evas/canvas/efl_canvas_vg_node.eo.cs
was previously undocumented because that property (inherited from Efl.Gfx.Stack)
has no docs, only its getter has docs.

Reviewers: lauromoura

Reviewed By: lauromoura

Subscribers: cedric, #reviewers, #committers

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D7500