Split mongodb_store launch file into two.

[hawesie]

This now provides mongodb_store_inc.launch which assumes that a machine tag has been previously set, and is provided by the machine arg. The original mongodb_store.launch file defines a machine tag then calls the _inc.launch file. This design minimises duplication as far as possible, but is still a bit inelegant. The reason we couldn't do everything with a single file, as discussed in #148, is we can't test whether an argument has been set in roslaunch so we don't know when to define a machine tag ourselves. The additional boolean flag to dictate this definition was not a nice solution either.

This supercedes #148

@furushchev please double check that this works for your use case. I assume you will include mongodb_store_inc.launch in your framework and pass the machine:=XXX arg to it.

@Jailander this should work with our setup, although we now are missing the use_machine argument as this is assumed to be true in the outer launch file.

[Jailander]

@hawesie it fine by me, we'll just set the use_machine in the tmux script, maybe a warning for all sites is needed too?

[hawesie]

@Jailander use_machine is now gone! The point is that now by using the original launch file we assume that this file will set the machine tag. Also looking at all this I really think we should start defining standard machine tags for STRANDS robots (e.g. main, left and right) and including them from a site-specific file.

[Jailander]

Oops, sorry read it wrong. Ok, that makes sense, in that case we will need to start changing all the launch files in the STRANDS system.

[hawesie]

Only the core one so far (if this is merged_. The more broad changes for machine tags should be discussed by a bunch of us first.

[furushchev]

@hawesie I checked it works without problem on our PR2 Robot, and on local laptop. I think it's ok! Thank you for your effort! :+1:

[hawesie]

I will now create a new release with this and the other recent updates.