add option to reset

[dpg2012]

I use multiple note types and limiting the columns to only relevant fields would be very valuable. Can you please implement one of the following capabilities?

• to remove/reset all current fields in one step (so only relevant fields can be added) or
• to allow the user to create presets for a given note type and replace current fields with the selected preset

Thank you.

[ijgnd]

for the presets option: see #134