fix(ngModel): test & update correct model when running $validate

If `$validate` is invoked when the model is already invalid, `$validate`
should pass `$$invalidModelValue` to the validators, not `$modelValue`.

Moreover, if `$validate` is invoked and it is found that the invalid model
has become valid, this previously invalid model should be assigned to
`$modelValue`.

Lastly, if `$validate` is invoked and it is found that the model has
become invalid, the previously valid model should be assigned to
`$$invalidModelValue`.

Closes #7836
Closes #7837
test(input): simplified $apply syntax
docs(error/$rootScope/inprog): fix $timeout typo

Closes #8071
fix(parseKeyValue): ignore properties in prototype chain.

Previously, properties (typically functions) in the prototype chain (Object.prototype) would shadow
query parameters, and cause them to be serialized incorrectly.

This CL guards against this by using hasOwnProperty() to ensure that only own properties are a concern.

Closes #8070
Fixes #8068
feat($q): add streamlined ES6-style interface for using $q

This potentially helps lead the way towards a more performant fly-weight implementation, as discussed
earlier in the year. Using a constructor means we can put things in the prototype chain, and essentially
treat $q as a Promise class, and reuse methods as appropriate.

Short of that, I feel this style is slightly more convenient and streamlined, compared with the older
API.