chore(pubspec): update pubspec.lock to match pubspec.yaml
perf(nodecursor): do not grow/shrink the nodes list

This also enables one to construct a NodeCursor with a fixed size list
of nodes.
style(ng-repeat): correct typing for nodes list
perf(dom): improve dom cloning speed
chore(forms): add demo for repeatable forms

Closes #1044
Fix HashMap undefined due to missing import

Closes #1280
perf(watch-group): remove expression coalescing

Coalescing is rare but slows down WatchGroup creation.

Closes #1328