Improve UX of Wiki Editor page
- Add a welcome message for first time contributor
- Add Help icons with links to relevant sections in Editor documentation
- Add explanations in page for Tags, Revision Comment and Attachments
- As Tags are now important for MDN search engine, moves them above Revision Comment
Merge pull request #2108 from tregagnon/improve-editor-ux

Improve UX of Wiki Editor page
Fix Bug 981395 - Update "Help improve MDN" links on front page
The usual periodic image compression crunch
Merge pull request #2120 from darkwing/image-squish-paris

The usual periodic image compression crunch
Use button instead of javascript:; a
Merge pull request #2113 from darkwing/attach-button-be-quiet-icaaq

Use button instead of javascript:; a
Merge pull request #2122 from tregagnon/bug-981395

Fix Bug 981395 - Update "Help improve MDN" links on front page
Merge pull request #2121 from jezdez/search-unicode-param

Fix bug 981397 - handle unicode query parameter content correctly.
Merge pull request #2119 from icaaq/mobile_padding

changed the padding on mobile to 15px, to fit in more content.
Update installation instruction to make them easier to understand the first time.
removed live sample iframe border
Fix bug 877423 - Clarify user ban in admin UI
bug 981274: Quick fix for ISE when $ used in macro names
Merge pull request #2128 from gorhgorh/master

removed live sample iframe border
Performance: Move TOC parsing into rendering stage
Merge pull request #2131 from lmorchard/performance-toc-html

Performance: Move TOC parsing into rendering stage
Fix wiki preview styled by old css.
Performance: Move parsing for doc summary HTML/text into rendering stage
fix bug 982174: Ensure build_json_data uses rendered HTML when available