Motion Paths GUI Cleanup

Over the past few months or so, it has come to my attention that the Motion Paths GUI had a number of issues which were confusing many people. For a few weeks, I've had a set of half-completed changes sitting around in my local repository for improving this situation, but had been stalled by a combination of the shorter release cycles and a heavy workload. However, last night I finally got around to finishing up this work (for a break/change), and committed it to SVN.

Highlights of the Redesign:

• Cleaner distinction between "settings used for baking" and "settings used for displaying". As per the original goals for the 2.5 Properties Editor and Toolbar, this has meant that settings affecting the next bake are presented as part of the relevant operators instead of being displayed in the Properties Editor (beside the "In Range" settings).
• Active display of the frame range of the baked path that the active entity (object/bone) is using. This should hopefully help to clarify why the path may stop getting drawn (the "cache" wasn't built to include those components)
• Calculate Paths operator now prompts about the range to bake. This should be easier than going through a whole bunch of different objects/bones ensuring that they are all set to use the right ranges. When combined with several bugfixes, most notably, the bugfix which means that existing paths don't need to be cleared before being recalculated with a different frame range, this makes using paths much easier.
• "Update" button is a convenience feature to avoid going through the popup baking settings. (EDIT: after writing this, I found a little bug here which I'll look into when I get time over the next few days). 

Now, there are some rough edges that need refining and which I'm not satisfied with yet. For example:

• I haven't found a nice way to deal with those checkboxes yet. Nothing quite looks right.
• Names of things probably need a second look.  

Anyways, this was just a quick writeup to draw attention to this. Please take a look, and let me know if this is better/worse or where some tweaks are still needed.

Cheers!