Fix #213

Show a hint when no morphology was selected for a token the user wants
to annotate with SG, but don't throw an error.
Introduce a hasChanged property to SG grammars
Add optional change notification in nestedMenu
More efficient change detection in sgAncestors
Update hint text in sG
Add arethusaUtil.empty() for arrays
Add collection watch in sgAncestors again

We have troubles keeping track of changes of morph on the fly.
Something is wrong with this plugin...
Minor refactor of SG
Less infinite digests in SG...
Get rid of collection watch in sgAncestors again
WIP
Oh my god, we need the watchCollection...
Add a cache for sg menu building
Reset morph properly in sG

Otherwise we're stuck with old info when we deselect a form!
Fix grammarReset in sG

The defining attributes cannot be changed in place now, as they are
cached.
Change MainCtrl.initPlugins()

Get rid of the try/catch which covers all errors that happen during an
init. This is more expressive and safer.
Fix typo in sg dative cases
Fix wrong dative nesting in sg labels
Fix key of command in infinitive sg labels
Fix state retrieval in sg