Use message logger in file IO code
Correct indentation error
Abbreviate RigUIControls to rig

Simply to shorten lines and perhaps make it easier if we rename the
module to be more pep-8 conformant.
Switch to ItemFactory from eval() method

Eval should be considered dangerous so we switch to a cleaner table
lookup mechanism for figuring out what classes to create from the text
mime data from the drop event.

We add .name class level values to the widget classes and construct a
table of name -> constructor pairs. This keeps the look up name nice and
close to the class definition.

We also change to using the .name attributes instead of the strings when
creating the DragItem controls to make sure everything stays in sync.
Code cleanup

Just white space changes and comments and "Select Markers" -> "Select
Guide Markers".
Merge branch 'itemFactory'
Neatened up WireGroup Curve draw - additional method

This still is in huge need of optimising, but an extra method has been
added to the node class that allows us to call the update from one method
call. This has allowed a couple of lines of code to be simplified down to
one call in a number of areas.