Fix for Propertiespane update problem

Mainly a fix for a problem where the variables on the Objectframe Input and Output tabs never update until you close and reopen the window. I found out from this post from Slickgrid's creator:

https://github.com/mleibman/SlickGrid/issues/168

how to solve the problem. The performance hit on this is much lower now.

1.) The above fix also eliminated the need to re-create the slickgrid and dataview whenever we switched context in the Parameters Pane. This was a major performance problem that we somehow never noticed.

2.) Changed the get_attributes function so that it only sends a slot dictionary if the comp actually has slots. This cleans up an error that was echoing to the console.

3.) Changed loadData to loadTabs. This was definitely an error, but I don't think we ever hit it. Must be an "state" that never occurs in our logic. I only noticed this accidentally when trying to figure out how to fix the original bug.