Stabilize API

[ammen99]

The plan for Wayfire has always been to rely heavily on external plugins for much of the specialized functionality each user wants. In order to make progress towards this goal, Wayfire needs to provide a stable API for external plugins, otherwise, many plugins will be written and then quickly get outdated without continuous maintenance.

Unfortunately, not all breaking changes can be foreseen at the current moment. However, we should have a plan for stabilizing the API:

• For the 0.8 release: include all planned breaking changes. This will likely mean that 0.8 won't happen very soon (all changes will probably take several more months) and that most plugins will get broken, but so be it. Single this will also mean that likely some new bugs will be introduced, these changes will be merged to the stabilize-api branch first, then merged together to master after some testing.
• After the 0.8 release: avoid major breaking changes at all costs. Examples of major breaking changes are transactions, Rework signal_connection_t #1307, Revamp view transformers #1308, Split view_interface_t #1309. 'Smaller' breaking changes like adding or changing parameters of single methods may still be done.
• Depending on how the previous stage goes, we may declare stable API before Wayfire 1.0

[ammen99]

This is now more or less done. There are no more major API changes planned for the next few years (hopefully), except for new features like color management which will likely require changes in the shaders.