Backport some PRs from brackets

[ficristo]

Look at master...adobe:master
Would be nice to retain the authors...

[ficristo]

• A bunch of them Backport #28
• brackets-eslint 3.2.0 Upgrade brackets-eslint to 3.2.0 (#13717) #32
• Some livepreview stuff Live preview #57
• Keep the search bar open Keep the search bar open #154
• Fix for FindInFiles UI not opening when no file is open Fix for FindInFiles UI not opening when no file is open (#14416) #157
• Context submenu and fix quick search overflow Cherry-pick context submenu and fix quick search overflow #168
• Changed WebPlatform License to MDN License Merge pull request #13447 from adobe/saurabh95/MDNLicenseUpdate #171

PR still open in Brackets that are integrated:

• Find whole word Find whole word #170 see [REVIEW ONLY] Add "Find Whole Word" Functionality adobe/brackets#9526
• New line and tab as replacement Added new line and tab as replacement in case of regex search #169 see Added new line and tab as replacement in case of regex search adobe/brackets#11614

[ficristo]

With #245 done, I merged everything back.