add a new copy feature in the sequencer view

[lpwisniewski]

While using the sequencer view, I often see myself copying part of a sequence to modify it slightly afterward. The current sequencer view doesn't let me do this easily. I tried to quickly hack the view to have the following behavior:

• While pressing DUPLICATE with a pad in the loop section, copy the selected page
• While pressing DUPLICATE and NEW wiht a pad in the loop section, paste the current buffer

This is a quick hack just to check if:

• The feature can be eventually added
• Get feedback on usability
• Get guidance to productionize it
• Get tester on other gears, I only have a Push 1

[git-moss]

Would prefer a generic solution and no quick hacks.