* refactoring assets management code
* finalizing refactoring of assets management
* various code review of new assets management code
* fix#2281
* fix#1961
* fix#1293
* fix#1275
* fix update scheduler timing logic
* forward compatibility (to be removed once 1.11+ is widespread)
* more codereview; give admins ability to specify own assets.json
* "assetKey" is more accurate than "path"
* fix group count update when building dom incrementally
* reorganize content (order, added URLs, etc.)
* ability to customize updater through advanced settings
* better spinner icon
Now splitting high-high generics in two subgroups: one group for
simple selectors, another group for complex selectors. Turns out
the great majority of high-high generics are simple selectors, and
simple selectors can be applied incrementally with DOM changes, as
opposed to complex selectors. This brings in a significant perf.
improvement in the processing of high-high generics (previously,
all high-high generic selectors were processed as one big complex
selector).
