Set the executable bit on runnable SDK scripts

Summary:
This lets us set up symlinks in webapp/tools that can run as, e.g.,
tools/appcfg.py.

Test Plan: ./appcfg.py now works.

Reviewers: dylan

Reviewed By: dylan

Subscribers: dylan, csilvers

Differential Revision: http://phabricator.khanacademy.org/D9865
Add change detection logging to the mtime and inotify file watchers

Summary:
The mtime and inotify file watchers will now emit a log message containing the
path of the changed file that is triggering a reload.

I'll do the same for the fsevents file watcher when I restore it but I'm not
going to touch the win32 file watcher.

Test Plan:
I tested the mtime file watcher on my Mac.

1. Started dev_appserver.py with the usual arguments for serving webapp
2. Ran `touch Makefile` and saw the log message "Detected change in Makefile"
3. Deleted and re-added the Makefile and saw the same log message for both
4. Ran `touch content/models.py` and saw log messages for content, content/models.py, and genfiles/kake-server.log

Reviewers: csilvers

Reviewed By: csilvers

Differential Revision: http://phabricator.khanacademy.org/D9084
Add lint_blacklist.txt

Test Plan: None