added backend users

[gerchomat]

added backend users with user #name, real name, email address, description, avatar (for TYPO3 7) and last login to fix #7

[georgringer]

Thanks for your PR! It would be great to create an issue first to be able to discuss implementation before the actual work is done.
Currently I don't know why I would need all be_users of clients at the monitor? Can you share some thoughts?

[gerchomat]

For us it would be a great feature to see all "old" and inactive be_users.

For example sometimes a co worker leaves the agency or something like that but his user sill exists.
Sometimes the users still exists a couple of years in several clients cause you don't have an overview about that.

So for us it would be a very good feature to cleanup the projects.

Although it would be a good feature to filter the users by user or real name over all clients to find the old users.

[beathorst]

I like this feature

[georgringer]

I don't see the need for having those as relations. I would just save those as text, maybe as a json holding information like usermame,isAdmin,disabled and name.

@beathorst please take a look at the 8lts branch which will be the next main version which requires all db calls done with doctrine