Merge pull request #51 from jerrywell/3.5

3.5
Merge pull request #52 from jerrywell/3.5

ZSS-690 Edit cell with text contains line break, it should apply "wrap-t...
Bug ZSS-762: context menu on sheet bar may be closed when we right click on the inactive sheet tab
http://tracker.zkoss.org/browse/ZSS-762
Merge pull request #53 from RaymondChao/ZSS-762

Bug ZSS-762: context menu on sheet bar may be closed when we right click on the inactive sheet tab
Bug ZSS-755: Press minus key, '-', cannot enter editing mode in a cell under firefox