1. freeze row (or columns) of each sheet independently with API by
passing row index (or column index).
2. unfreeze rows (or columns) of each sheet independently with API by
passing -1.
For new data structure of freezing rows (columns), re-implement spec
about 
* inserting and removing rows (columns)
* max visible rows changes
change implementation. We store frozen rows (columns) information of
each sheet in Spreadsheet component instead of client-side. Hence, we
ignore data from client.
add test app for ZSS-206
refine test app for ZSS-206