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
Merge remote-tracking branch 'origin/development' into newpog
Merge remote-tracking branch 'origin/ldc/astntrw' into newpog
Merge remote-tracking branch 'origin/newpog' into development
Enabled interpretation of type bindings e.g. i : int.

require sync with overturetool/overture@9b69777c31e28171aac7228954a0840f24157634
Update state invariant PO results.
UPdated atomic assignment PO test but it's still a bit broken.
close #263 added check for return
Merge commit '9c95c6fae7487bc7f3364de05b7fc11df8953b01' into development
Merge commit '064a80127a0ad142becec2cd8ff5b3192e44e7af' into development
Comment out stray `return` in a test