Add a DDS communication layer; needs external code generation for ful…

[jwalt]

This is a draft of a fully working, type-safe DDS communication layer. It needs external tools to compile, as the type definitions are generated by command line tools of the DDS library.

With this draft PR, we would like to request comments about the general approach.

[cochicde]

wow! nicely done! however, for me is quite hard to separate the examples from and generated files from what's would actually end up in forte's code.

I'd recommend leaving the example independent code under src/com. The .idl and .msg files are also not forte-related and the .cxx are generated so they shouldn't be important to understand the integration.

The example_message/StringDebug seems small enough to see the integration. I'd recommend having this maybe under the test folder.

Also, there's some embrick/sysfs changes which seem not to belong here

[jwalt]

sorry, rebased it to the wrong branch. sysfs stuff is gone :-)

[gravemalte]

Right, the generated files are not forte related, they got published because otherwise the examples would not be able to run (and we want that you can try it out. Without the files, it is quite complicated to get everything fully working, a lot of code generation happens in the background). The plan is that you just write an .msg file put it somewhere and the whole generation process is integrated into the CMake build process. The whole thing needs some clean-up, but is a first proof-of-concept. If you have issues with running the examples, let me know.