🐾 Add "copy from template" feature when editing a mapping

[yaacov]

Issue:
When editing a mapping a user may want to copy an existing mapping template

Fix:
Allow a "copy from template" option, allowing a user to choose a template
when a user choose a template the current mapping will reset to use the same mappings as the template.

Notes:

• Allow to use only templates that are on the same namespace or "default" namespace
• Alow to use only templates defined for the same source and target providers
• Once mapping is copied, a user can edit the mappings again

[yaacov]

adding @dgur for visibitly