UC-18 - Central repository of templates

[cudeso]

Provide configuration for a central template repository (URL, credentials, sync settings).
Implement listing and viewing templates from the central repository.
Allow adding templates both from the local template system and directly from the central repository menu.
Implement submission of local templates to the central repository and synchronisation of templates down from that repository.
Log template repository interactions in the audit trail and enforce TemplateEditor permission for these actions.

[cudeso]

flowintel/flowintel#124

[cudeso]

• Can be great to have a button in the collapse part of a repo next to case/task templates to import all in one click
• When a scan is made, a repo is added, run a refresh directly
• Add a html title on uuid and case/task title in case they are truncated
• Lot of "local" function can be moved in common_template_core.py
• Action on DB may can be done in TemplateCase.py/TaskTemplateCore.py
• Clone a repo when adding it using "add a repo" button when giving an url