transition: move agency/line/etc duplication operations to the backend

[tahini]

The *Duplicator code is executed in the client, which sends a lot of queries to the server. It could be done directly by the server instead of individually sending all the data there, one object at a time.

The steps for this issue are

• Duplicate services in the backend #939
• Duplicate lines in the backend #940
• Duplicate paths in the backend #941
• Duplicate agencies in the backend #942
• Duplicate schedules in the backend #943
• Duplicate nodes in the backend #944
• Duplicate scenarios in the backend #945

The first 5 are the critical ones as duplicating an agency requires all of them and that operation should be "atomic".

[greenscientist]

Also, the current situation mean we need to trust whatever happen in the client for data integrity and security

[tahini]

client data who could be out of date...

[greenscientist]

Just bumped into this again, it would be a great optimisation, it's quite long and error prone at the moment

[tahini]

@greenscientist funny you bumped into this 5 days ago, and I'm bumping into it today from a totally different investigation. I guess the universe decided...