WIP: perf(ngInclude): cache linkFns for each template

This is probably not the best way to do this but here is a working Proof of Concept.

See http://www.bennadel.com/blog/2738-using-ngrepeat-with-nginclude-hurts-performance-in-angularjs.htm

Here is demo: http://plnkr.co/edit/Pf9DVKxNEAZQavcGm7Bu?p=preview
If we compile things here, why are we keeping `ngIncludeFillContentDirective` ?