perf: use call and === instead of apply and == in type check functions

Updates isDate et al to use call instead of apply and === instead of ==.
The change to call brings minor performance improvement and === is just
better practice than ==.
http://jsperf.com/call-vs-apply-tostring

Closes #5295
perf($resource): use shallow copy instead of angular.copy

Replace calls to angular.copy with calls to a new function, shallowClearAndCopy.
Add calls to copy for cache access in $http in order to prevent modification of cached data.
Results in a measurable improvement to the startup time of complex apps within Google.

Closes #5300
perf(a): do not link when href or name exists in template

Change the a directive to link and hookup a click event only when
there is no href or name in the template element.
In a large Google app, this results in about 800 fewer registrations,
saving a small but measurable amount of time and memory.

Closes #5362
perf(jqLite): implement and use the `empty` method in place of `html(‘’)`

jQuery's elem.html('') is way slower than elem.empty(). As clearing
element contents happens quite often in certain scenarios, switching
to using .empty() provides a significant performance boost when using
Angular with jQuery.

Closes #4457