README: Clarify support for future Lua implementations
README: Start reorganizing the API documentation

This patch starts the process of breaking down the API documentation
into chunks of different examples, each showcasing a different part of
the library.  This patch also adds an example for enabling and
disabling actions and how that compares to simply removing actions.

The full list of methods includes ‘removeActionInterval()’, which does
not currently exist.  That is an oversight that a future patch will
address by implementing it.
Implement removeActionInterval()

The other ‘set’ methods have related ‘remove’ methods, except when it
comes to setting the interval of an action.  This patch corrects that
oversight in the API.
Improve the source-generated documentation, especially about actions

This patch makes large changes to the source-code comments so that
LDoc (or LuaDoc) will create more detailed information about Luvent,
and specifically the internal ‘Action’ objects that we use.
README: Finish filling out the sections of example usage

This patch also removes the warning about the stability of the API
because I am close to cutting and releasing the first version.
LuaRocks: Version 1.0.0-1