parseHTML: fix whitebox selector

Conflicts:
	shared.js
parseHTML: fix group wilting count regex
fix a bug where new groups regarded as disabled
opts: use Memrise.getDB
update CHANGES.md
parseHTML: set course wilting 0 as default
fix .jshintrc
update assets/home.html
main: set button based on settings model

- no disabled courses: works
- disabled courses: should work
- some things not tested
topics: use a custom rivets binder to disable/enable checkbox
opts: refresh when settings change is fired

- settings no longer fires change when resetting to defaults
main: regard groups with all disabled courses as disabled
main: handle zero wilting plants with disabled courses
main: handle empty enabledGroups
server: serve root
Merge branch 'master' into options-rewrite

Conflicts:
	CHANGES.md
	main.js
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