bootstrap: remove css load nonsense
bootstrap: cleaning script load logic
ide: config setting to control whether to use codeeditor completions
ide: completions are again computed in worker code. This won't prolong loading and will use all avaiable sources for word completion computation. Eventually this will be moved into a subserver.

reverts part of #9d131d7 and #1fc1ba3
bootstrap: allow JS scripts to be loaded via script tags again. This fixes cross-domain code loading and JSONP support. Also remove Global.livelySources as it is not used by completions anymore