hide QM on the Hooks list

`define( 'QM_HIDE_SELF', true );` to enable
Some focus styles for the admin toolbar and toggle links.
Added support for Google App Engine, Fixes #73

Using DirectoryIterator rather than glob in order to support Google App
Engine for PHP (tested on 1.9.10 - 2014-08-28).
Introduce a `tear_down` method for collectors to avoid further unnecessary collection during QM output. Fixes #76.
Merge remote-tracking branch 'origin/develop' into develop
Split SQL queries on LEFT, OUTER, and RIGHT too.
Use a tilde instead of an ellipsis when truncating a path.
Gracefully aovid fatal errors if a site is moved and the db.php symlink is no longer pointing to the correct location.
Better handling of unknown components (this still needs a refactoring).
Pause Infinite Scroll when Query Monitor is viewed. Thanks to @scottsweb for the idea.
Merge branch 'aidanlane-master' into develop
Introduce context for a component, improve performance when not showing QM's own actions in the hooks list.
Merge branch 'szepeviktor-master' into develop
Better variable names for hook parts and components.