hotkey_bindings treated as json
read hotkey definitions from  hotkeys.json
comment out bad json file read
new hotkey command: set_jumpsize for transport jump
new subroutines jump_forward(), jump_backward() use $text->{hotkey_plackback_jumpsize}
This reverts commit 551a887d6028d50f47457f09b18a1f98d91c28c5.
Revert "comment out bad json file read"

fixed source file, so dont need this
use Data::Dumper to dump custom.pl
correct data structure
hotkey_bindings: convert to json
add build dependency Text::Template
command description
Edit: increment n attribute serially
Track restore: ensure current_edit field is initialized
don't remove mark if in use by fade