Handle list of bitstrings present in model, quite common for mongodb

Currently there was no way to edit and update list of strings
this has been taken care of by
1. adding a metadata called list fields in the model
2. all list fields are displayed in csv format
3. when editing the list fields will be split by comma and then pushed
to db

Signed-off-by: himangshu <himangshuj@live.com>