drag and drop local zip file install for ExtensionManager
refactor install status logic to new Package.installPath() method. add flag to keep local zip files.
UI from @larz0. Refactor from table view to dialog.
revert changed to ExtensionManagerView
use LESS color variables
Dutch language updated (2)

Why it won't work the previous time?
Added missing SHA
Merge branch 'master' into adobe-jasonsanjose/extension-install-draganddrop

Conflicts:
	src/styles/brackets.less
Redoing the dark theme to be more plain CSS and not rely on central variables.
Fix inline editor colors.
Use correct error message when renaming/deleting folder
Unified error message function, Title cased strings
Use ERR_TYPE_* constants
Consolidate all error dialogs into new method
Title Case FILENAME and DIRECTORY_NAME
Use switch, review changes
code review comments
Merge branch 'jasonsanjose/extension-install-draganddrop' of https://github.com/adobe/brackets into jasonsanjose/extension-install-draganddrop
Merge pull request #8462 from adobe/dangoor/8420-theme-rejigger

Redoing the dark theme to be more plain CSS and not rely on central variables
jsdoc: add @constructor tag