clean up cell_def_cycle_tab.py

[rheiland]

Now that CycleTab is a subclass of CellDefSubTab, let's eventually clean up confusing uses of objects, e.g., self.celldef_tab.param_d vs. self.param_d

[drbergman]

Yeah, I feel like I just shoulda done all this or kept it all as one file. Instead, I left it in this weird state...

For the record, those two dictionaries are the same dictionary. The solution I've considered here is each mini-tab getting its own dict, which would just mean refactoring the fill_xml and fill_gui functions to have tab-specific versions. refactor so that we pass uep's around to avoid any xml-reading overhead (if that's at all a concern)