exec_redcap_locking_data forms.py improvements

[gcyoung1]

1. There should be an option to lock/unlock all forms for an event
2. There should be some form validation:

ncanda@pipeline-back[pipeline_back_1]:/sibis-software/python-packages/sibispy/cmds (master)$ python exec_redcap_locking_data.py -e 7y -v --lock -f test_invalid_form
Connected to REDCap using: Engine(mysql+pymysql://root:***@192.168.1.1:3306/redcap)
Visit: 7y visit
Attempting to lock form: ['test_invalid_form']
The test_invalid_form form has been locked
Record of locked files: /tmp/locked_records.csv
Done!