Need to make mbRestore command more user friendly

1. Instead of listing all the sqlite db files with full path, which is tedious and error prone, it is more easier to just say the source directory and bucket name and let the script to figure out all applicable db files. This will be consistent with how we specify arguments for mbbackup command.

2. it is desirable to have some stats data at the end of run, say, how many added, updated, or skipped.