sanity checks to prevent null pointer exception
save to history only after press of run button; fixes #37
cell sorting key is now favourite+rank+case; replace onCheckedChange
with onClick listener---appears to be common pitfall; implements #25
prefill group field with current group name; fixes #34
implement CellCollection.cleanHistory(); add clean history menu item;
fixes #26
fix unexpected behaviour in cell cpy ctor
remove default in switchToGroup(); part of move to #41
on phones after cell discard, go back to base
remove random rank assignment
we really shouldn't return null if a String is expected
always clear groupCache after cell removal; fixes #38
remove irrelevant code
immediately save after long click dialog; fixes #45
bump version, changelog
Merge pull request #42 from rwst/dev

fixes, enhancements, version 0.9.3