docs($q): fixed spelling, removed extra characters

Closes #8779
docs(FormController): document $submitted property

Closes #8732
docs($rootScope): remove duplicate `$digest()`

Closes #8840
perf(select): execute render after $digest cycle

This is an optimization to defer execution of the render function in the
select directive after the $digest cycle completes inside the
$watchCollection expressions.  This does a check to see if the render
function is already registered in the $$postDigestQueue before it passes
it into $$postDigest, guaranteeing that the DOM manipulation happens
only in one execution after the model settles.

Closes #8825
fix(currencyFilter): pass through null and undefined values

When these special values are passed through one-time binding will work correctly.

BREAKING CHANGE: previously the currency filter would convert null and undefined values into empty string, after this change
these values will be passed through.

Only cases when the currency filter is chained with another filter that doesn't expect null/undefined will be affected. This
should be very rare.

This change will not change the visual output of the filter because the interpolation will convert the null/undefined to
an empty string.

Closes #8605
fix(numberFilter): pass through null and undefined values

When these special values are passed through one-time binding will work correctly.

BREAKING CHANGE: previously the number filter would convert null and undefined values into empty string, after this change
these values will be passed through.

Only cases when the number filter is chained with another filter that doesn't expect null/undefined will be affected. This
should be very rare.

This change will not change the visual output of the filter because the interpolation will convert the null/undefined to
an empty string.

Closes #8605
Closes #8842
fix(ngSwitch): avoid removing DOM nodes twice within watch operation

Closes #8662