InsertCurrentTime: don't fiddle with the cell while editing

Change-Id: Ia12b10a44b7d90344a009753ddae801b7d58dddf
current date/time hotkey inserts also if cell is in input or edit mode

Change-Id: Ib3caed607a5ca1b5ce82de0472223c7bdc8f7f54
treat datetime as handled

Change-Id: Idc94174662eee5a75a6b467e47cbf9027e3ba224