User input for egocentric alignment indexes

[katiekly]

I noticed in the Data Organization tab of the GUI, the maximum value is hard-coded to 5. The max index value should be automatically set to the # of bodyparts found in the csv files. In this case, it would be 8.

Can you also include a similar warning if the user enters the same index value in both fields. Currently, I can continue the next steps but this should not be the case.