dropbox_overbyrn.plg: change dropbox_install function by creating two conditional sections for the make, chmod & chown commands. This is because the install routine is also called during an enable and this causes unnecessary delays during plugin startup when a user has a large number of files and folders in their existing dropbox directory.  See thread : http://lime-technology.com/forum/index.php?topic=23287.msg272879#msg272879 for more details.

Thanks to capler for testing.

Bump plugin version to 1.3c