Add examples of configuring proxy and scripts.

It can be hard to appropriately set these settings when using uzbl for
the first time.  Add appropriate usage to the example config for easy
configuation.
Fix Python installation with an empty DESTDIR
Merge remote-tracking branch 'gh/ToBeReplaced/enable-scripts' into mathstuf/next

* gh/ToBeReplaced/enable-scripts:
  Add examples of configuring proxy and scripts.