First import of Apps Developer Tools from Chromium source code.
Set size of icons to 48x48
Removed unused file.
Added missing CSS files
Added missing images
Removed conditional CSS rules
Merge pull request #1 from dinhviethoa/first-import

First import of Apps Developer Tools from Chromium source code.
Merge pull request #4 from dinhviethoa/3-icon-size

Fixed #3. Icon size of apps and extension is forced to 48x48.