Plugins loading and selection policy.

[Plaque-fcc]

The discussion on how should be the plugins loaded could be cross-linked and discussed here further.
luakit/luakit#147

[Plaque-fcc]

From luakit/luakit#155
Can unify URI analyzers in a pack. Supposed to affect adblock, introduce customhosts, something else.

[aidanholm]

There's also luakit/luakit#219
Perhaps we should open a project to consolidate issues about this, or have one mega-issue and close the others? I'm definitely interested in moving towards a more advanced plugin system, but it's hard to keep track of all the issues :)