Resolve path of relative plugin directories relative to root

  - Change the way the plugin directories are resolved,
     instead of being relative to the current working
     directory they are now relative to the root of
     the main DDRPi script, meaning that it can be invoked
     from anywhere, no longer just in the root directory
Add initial version of the patterns plugin

  - Ported the existing PatternsVisualisationPlugin
     to the new format and added a directory of its
     own to store the various CSV files in
Change function arguments to not unpack tuple

  - Python 3 doesn't like have foo( x, (y,z)) as a function
     definition, so changed draw_controller to unpack them
     explicitly in the function
Conform with Python 3 division

  Ensure that parameters that need to be ints, are ints
Change print calls to print() calls where necessary
Remove reference to itertools.next() which has gone in python 3

  - Replace .next() with next(..) which works in python 2.6+
Add .gitignore

  - Ignore compiled python files and vim temp files