Add C glib builders

[kszucs]

Steps (these could be documented in projects/arrow/README.md):

1. Add a new docker image with the required dependencies added, based on the cpp one.
2. Build the image(s) via ursabot docker -n c_glib build (assuming that the image is named as c_glib).
3. Add a builder based on the CppTest builder with c_glib specific steps and properties.
4. Add it to arrow's master.cfg
5. Configure a scheduler with the appropiate file change paths (cpp/* and c_glib/*)
6. Add an entry for the builder in the .travis.yml to test it automatically.

@kou would you like to pick up this issue?

[kou]

OK.
I'll work on this.

[kszucs]

Let me know if you've stuck with anything!

[kou]

I've created #172.
I used c-glib than c_glib for image name because we already use - in cpp-benchmark.