Support for RP1000

1) Add missing support for DELAY_TAP_TIME, DELAY_MULTIPLIER, and
   AMP_LOOP_ON_OFF.

2) Add a warning when get_modifier() fails.

3) In update_modifier_linkable_list(), set label to "Unknown" when
   the lookup of a modfier fails.

4) In format ipv(), the warning message that's emitted if get_xml_settings()
   fails reversed position and id.

5) In update_modifier_vbox(), remove the assert that the group label is not
   null. Set the combo box text to "Unknown".
Fine tune debugging.

1) If get_modifier() fails, set the label to "Unknown pos/id". Thus, label
   will always be non-null and debugging should be easier. The minor downside
   is that the label string is leaked when we update the modifier group.

2) Restore the assert in update_modifier_vbox() and the now unnecessary
   test of group[x].label.
Merge branch 'master' into rp1000
Merge mainline RP1000 changes.
Remove duplicate RP1000 code.

Support for RP1000 has been merged upstream, so the rp1000 changes
in this branch are unneeded.
Restore modifier for delay tap time 4990.
Fix up some whitespace.