Would be handy to disable fetching of RDS data

[benchub]

I know I don't want to use pygmy with RDS at the moment - it would be good to disable looking for such instances.

[AadiMehta]

python manage.py populate_settings_data now asks for this configuration

SHA-1: 2fb166f2fb52b1fd8e45151bffc80e55244c9237

• Changes:
  1. Populate settings now ask for which regions to enable sync of
  2. Populate settings can now configure secrets
  3. Populate settings can now enable/disable RDS/EC2 sync
  4. Case correction
  5. Pygmy now using the right db credentials