Automatically add rows/columns when copy-pasting cells from different spreadsheet

[apawlik]

A newly opened Stencila Sheet has 10 rows and 21 columns. When copy-pasting more than 10 rows / 21 columns from another spreadsheet application, the data gets truncated to these 10 rows / 21 columns. A user will expect the data to be all copied and Stencila Sheet to automatically add more rows columns.

Temporary solution could adding at least a warning ("Only 10 first rows / 21 columns will be copied").

[obuchtala]

Thanks! Will work on that.

[obuchtala]

This ready as a PR in stencila: stencila/stencila#651

[nokome]

FIxed