Changed "undefined" to "undef" as the former clashes with Isabelle's own undefined keyword.
Added PO loop functionality; in theory we can detect that the Isabelle command associated with a given PO has successfully finished and update the PO status. Unfortunately this status does not appear to being updated in PO list viewer as such.
Merge remote-tracking branch 'origin/sdf' into ldc/tipi

Conflicts:
	ide/plugins/theoremprover/src/main/java/eu/compassresearch/ide/theoremprover/TPPluginDoStuff.java