update all the template parts for RUN

[SylvainTakerkart]

Following up our work with confocal microscopy, all the RUN template parts should be updated so that the variable names associated with all their fields should start by run_', or run_01, or run_02` etc.

This is aimed at facilitating the job of the BIDSification code (i.e finding more easily the different fields!)

[SylvainTakerkart]

this has been done in #21 !

however, I'm wondering at this stage whether the explicit field RunNumber should be kept... I believe that it can be deleted because:

• in BIDS, the value of a run is an index, i.e a positive integer (not a label with text)
• the information is already present in the name of the template part itself...

deleting this field would simplify the life of the users; however, in our current BIDSification code, that relies on our in-house multiple-export of the elab metadata, where this info is not directly available (because the name of the groups are not there...)

...to be thought about a bit more before deciding!