plugins package conflicts with built-in package in 1.7

[sbliven]

Pymol 1.7 includes a 'plugins' module (http://sourceforge.net/p/pymol/code/HEAD/tree/trunk/pymol/modules/pymol/plugins/). This conflicts with the 'plugins' loader package here.

The name should probably be changed to something like 'pymolplugins' (used internally as the package name). Note that this will require users to update their .pymolrc with the correct import statement.

[andwar]

this is resolved by adding paths to the plugin manager see #54