`io/lab`: Add remote io exercises

[Alex-deVis]

Added C equivalent exercises for remote-io and client-server model sections.

Depends on #295. Closes #136.

[Alex-deVis]

I applied your suggestions and dealt with most of the checkpatch.pl errors. Only two error kinds remain:

• [flake8] F401 'socket' imported but unused which complains about the socket import in the skeleton
• [cpplint] build/include_subdir which complains about the lack of a directory in the include path

I suggest we do not check the support/ directory for unused imports / variables to get rid of the first error. The second error should be removed as it does not bring any improvements.

[teodutu]

* `[flake8] F401 'socket' imported but unused` which complains about the `socket` import in the skeleton

Let's ignore this one.

* `[cpplint] build/include_subdir` which complains about the lack of a directory in the include path

Haven't we removed this already?

I suggest we do not check the support/ directory for unused imports / variables to get rid of the first error. The second error should be removed as it does not bring any improvements.

No. If anything, create a local CPPLINT.cfg file inside the problematic folders and use it to ignore certain filters / files.