Better track status of training data

1. Now we only allow clients to train for TEXTUAL data. For remaining types: we notify admins like devanshu via email and show clients that the data has been added for processing and will take a few days, you will be notified on email once its done. - Add reminder emails for admins that "x" training is still pending 2. If training fails at node end: store reason for failure and show it on dashboard (only gods can view this) 3. add basic validation: - checking column names for CSV - checking empty pdf Return early from laravel and do not proceed with (notifying admins) if the above fails