Added selector `splat` aliases, which expand based on arguments.

Similar to what happens in the forms and aria plugins, but easier to author.
Selector alias definitions are now automatically wrapped in `:any()` if	they are comma separated.
Updates following on from selector alias changes.
Added a directive capture method to simplify common uses.
Moved plugin adding of selector aliases to the process layer.

Removed unnecessary plugin disable callbacks.
Changed function registry to be per-process.
Reverted automatic `:any()` on selector aliases.
Some refactoring of the internal functions API.

Fixed issue with HHVM file_get_contents failing.
Reverting to colons for declaration aliases now hhvm has fixed its ini parsing issues.
Adding hhvm to the CI test config.