Stop mouseDown event from propagating.

Closes #2459
Remove semicolons
add troubleshooting long path issues for Windows
better script/clean removal for windows

Now `script/clean` uses `del /F /Q /S` to cleanup the folders but `del /S` deletes specified files from all subdirectories, so if we pass a folder as a parameter it will only delete the files within the folder and all subfolders recursively but not the actual folders. And this can cause problems, see Issue #2487

A better way is to use `rmdir /S /Q` as it takes care of the folder itself and it's contents.
/S - removes all directories and files in the specified directory in addition to the directory itself. (removes the directory tree)
/Q - obvious this is quite mode

I tested this approach on a couple machines that needed a clean before building and works OK with `rmdir`. It might give a warning in the console like `The system cannot find the file specified.` because not all of them are there but it can be ignored as the script will finish running.
Put the .editor class on the wrapper, not the component

Things depend on the react editor wrapper having the .editor class,
but inside the editor, we can control the style. I changed the
component's div to be .editor-contents for now. We can eliminate this
extra style when we eliminate the wrapper.
Make cursor visible when .editor-contents is focused
Use proper variable name
Upgrade to atom-package-manager@0.66
Merge pull request #2531 from radum/master

better script/clean removal for windows
Merge pull request #2522 from atom/cj-fix-react-double-click-bug

Fix unresponsive text input after double-clicking
Only spawn removed command for paths that exist

Prevents errors being logged when trying to remove folders that
don't exist on Windows.
Return early when skipping remove command
Upgrade to language-c@0.16.0
Upgrade to language-gfm@0.39.0
Upgrade to markdown-preview@0.74
Upgrade to apm 0.67
Upgrade to bracket-matcher@0.43
Upgrade to apm 0.68
Prepare 0.102 release
Upgrade to image-view@0.34