Persistent custom menu for DM42

[fossy]

Hello,

I like this extension and found it very useful.

But I think there are some things to correct:

- EXITALL does not return to CUSTOM menu - but the next key press will show the CUSTOM menu

- PRGM mode: I've used the keys [up] / [down] to browse through the program - this is impossible with the CUSTOM menu. It is possible to switch to the System menu with [CUSTOM] and use so [up] / [down] for program browsing

- perfect would be an configuration of this behavior On/Off persistant CUSTOM menu at all and On/Off CUSTOM menu while PRGM mode

The persistent CUSTOM menu is very useful!

Thanks!