docs(core): add note that isObject returns true for arrays

Closes #6353
docs(ie): document IE style attribute interpolation problem

IE has issues with this, it's good to make a note of this.

Closes #6329
docs(guide/directive): add a more detailed description of isolate scope `&` bindings

More description of "&" bindings, the fact that they trigger evaluation of expressions in the
original scope's context.

Closes #6255
docs(ngSubmit): reference correct object ($scope) in example.

Switched from this to $scope. It's confusing using $scope and this interchangeably.

Closes #6375
docs(guide/ie): correct conditional comment to load JSON polyfill for IE7 and lower

Text specifies "polyfill JSON.stringify for IE7 and below" conditional comment for loading the
polyfill was "lte IE 8".

Closes #6227