Add startProxyingInUiAndConfig function

i.e., parallel the changes made by stopProxyingInUiAndConfig on the
client side
removed PROXYING_STARTED update

also added new updates for start/stop providing proxy
Merge remote-tracking branch 'origin/dev' into lucyhe-update_icon_when_proxying

Conflicts:
	src/generic_ui/scripts/ui.ts
merging
Use accessIds to see if user is providing proxy
Remove Updates for start/stop providing proxy
Remove unused core.onUpdates
Remove startProxyingInUiAndConfig from API
Comments + small changes
Tiny edits
Removed stopProxyingInUiAndConfig from UIAPI
Edited variables/comments for clarity
Merge remote-tracking branch 'origin/dev' into lucyhe-update_icon_when_proxying and fix tests

Conflicts:
	src/generic_ui/scripts/ui.ts
Fix tests

Chrome connector tests broke after changing ui to UI.UserInterface
Added tests for extension icon changing
Merge pull request #452 from uProxy/lucyhe-update_icon_when_proxying

Update extension icon when giving access to or getting access from others