docs(readme,guides): add perf guide for IE. updates and corrections. (#11262)

- refine the IE performance guide
- make the IE performance guide visible in the docs
- indicate 1.4.x as minimum version to line up with bower-material
- update branding in screenshot to AngularJS
- update PR and issue templates
- major updates to the Contributing guide for clarity and consistency
- remove text about the project being in early beta
- make it clear that we are not accepting major new feature requests
- clarify issue submission guidelines to use GitHub templates
- provide better examples of issue titles, commit messages, etc
- add details and clarity to the commit levels and team roles
- minor updates to the PR guide

Fixes #8616. Relates to #8658. Relates to #8329.