LB-1819: Concurrency plugin refactor.

Added all-plugins.js
Now plugins are loaded and applied based on the theme.
Plugin must return an object { init: function(config, liveblog) ,[deps:
[] ]}
    compose of init key witch is the function to apply, witch accepts
config and liveblog parameters.
deps is optional and is an array of dependencies plugins.
    Deps plugins are applied if not applied before ( by other plugins or
by theme)