Configurable function keys, a first test

New entries in pipedit.cfg:

 F1=Help
 F2=
 F3=END
 F4=
 F5=RFIND
 F6=
 F7=UP
 F8=DOWN
 F9=
 F10=LEFT
 F11=RIGHT
 F12=RETRIEVE

Which means, there will be a working RETRIEVE command in the next release.