Update pog icon to a delta symbol.
More PO list column tweaking.
Initial working implementation of Isabelle session kill.
Remove unused imports.
Merge remote-tracking branch 'origin/development' into newpog
Check parsed function signature type to ensure it's actually a function
type, otherwise throw a StuckException.
Fix #229, Fix #256
Remove assistant calls from CmlLexNameToken.

This means a new (possibly less eficient) way to compute name token hashcodes.
But it has to be done since we will not thread assistant factories into name
tokens.
Replace static calls to PAccessSpecifier astnt with factory calls.
Thread assistant factory into PTypeSet constructor.

This copes with the latest changes to the overture assistant mechanisms.
Merge remote-tracking branch 'origin/development' into ldc/astntrw
Merge remote-tracking branch 'origin/development' into newpog
Merge remote-tracking branch 'origin/ldc/astntrw' into newpog
Analysing Insiel's example from Paolo.
Merge remote-tracking branch 'origin/development' into alrd
Merge with origin/alrd and improvements to remove tock events in analysis that do not use time.
Added Insiel's example from Paolo.
Merge remote-tracking branch 'origin/kel/base' into development
Merge remote-tracking branch 'origin/ldc/astntrw' into development
update test of unspecified operations to include public qualifier due to
upstream change to typechecker
Merge remote-tracking branch 'origin/newpog' into development