docs(guide/directive): explain how to require multiple controllers

Closes #8524
docs(guide/migration): ngSanitize is out ng core at AngularJS 1.2.21

When using ngBindHTML directive, either ngSanitize or $sce must be used
or this will end in a non-trusted value error.

Closes #8519
docs($http): fix broken markdown link in withCredentials description

Markdown typo in $http config documentation

Closes #7859
docs(http): don't use locale-specific uri for MDN link
docs(tutorial/step-10): add mock image data to spec

Closes #8468
Closes #8535
revert chore(Scope): remove deregisterNotifier feature for $watch

This reverts commit d2f8f25af2c078c971c7223a8894a01e0595cd20.

Closes #8542
revert perf(Scope): remove the need for the extra watch in $watchGroup

This reverts commit 28540c804a1b2e4dd3328b3caca1391c696da1ca.
fix(Scope): add deregisterNotifier to oneTimeLiteralWatch signature

A reverted commit removed deregisterNotifier from the arguments that would be passed
to a watcherFn.