Add validation to submission builder

[kcs3]

This includes changes to the GUI, and also to the server-side code and installation to run the validation script and report the results back to the user.

[zhouji2013]

Here are some details:

Actual validation is done by a python script. The implication for the deployment is:

1. a python 3 installation should be available from the server
2. the python script itself needs to be part of the deployment (or available from the server)
3. the background data (the subdirectory 'subject_data' in the current CTD2 dashboard data package) needs to be part of the deployment (or available from the server)

Validation can be done for two targets via their respective triggers:

• For a template entered using this builder, validation is an option in the dropdown menu from the template list page
• A zipped file can be uploaded to be validated. The validation report is displayed, but data will not be imported in this builder.