[#91] Consolidate all harvest source reindex code in a single action

Make it available to users with permissions on the harvest source
[#91] Remove config fields from source dict before indexing

We don't need them and will avoid indexing errors
Merge branch '91-reindex-list-fields-in-config'
[#88] Add redis to requirements
Fix variable not defined
Always remove harvest extras on after_show if there

Up until now we where relying on `for_edit` being present in the
context, but this is only added on the controllers. It's better to be
safe and remove them always. If needed (at index time) they will be
added afterwards.