Stim interface, StimEditGUI changes (#55)

* prevented ArgClass Extract from indexing into empty list

* FuncCallClass GetInputs and GetOutputs convenience function for returning strings

* GetProcInputs method returns all properties of ProcInputClass for use with proc stream checking

* Processing stream is only run if Check returns zero, else an error msg is raised

* Changed uses of properties to propnames in ProcInputClass GetProcInputs

* Added removal and addition of stim data columns and interface in StimEditGUI; added dialog box for setting amp, duration, and values for new stims

* Added rename column interface

* GUI updates: column interface changed, rename condition moved to menubar -> tools

* Tooltip to manual edit, exit condition for value entry prompt

* Generate filters with butter interface, error checking

* Logic to prevent button presses when no conditions are present

* Removed rename cond and add/delete/rename column GUI options because they result in undefined behavior