docs(error/$rootScope/inprog): improve understanding and diagnosis of the error

See #5549
docs(guide/databinding): add line breaks after images

This looks much better, thanks a bunch @NV

Closes #7748
docs(CHANGELOG.md): remove mention of strict-DI from v1.2.17

Strict-DI feature was originally merged into v1.2.x, but was reverted by https://github.com/angular/angular.js/commit/373078a94cf3d525b9ae11a2f2876acb6e26f6a3
Merge pull request #7 from angular/master

update