Issue #312 - grid group interface completed

1. Grid group interface completed: 
getTitle(), 
removeTitle(), 
setTitle(value), 
clear(), 
remove(), 
getRows(), 
appendRow(row), 
insertRowBefore(newRow, exitingRow)
refresh(rows).
2. Revised some functions in previous pull requests.
3. Tested on both ripple and device. It works well.
4. You should be able to pull in changes from this new branch. It is ahead of the master branch.