Angular 1.x -> AngularJS
Angular 1 -> AngularJS
Angular1 -> AngularJS
Angular 2+ -> Angular
Angular 2.0 -> Angular
Angular2 -> Angular

I have deliberately not touched any of the symbol names as that would cause big merge collisions with Tobias's work.

All the renames are in .md, .json, and inline comments and jsdocs.

PR Close #14132