Find dependencies with cmake find_package

Some dependency should provide a cmake config to use directly and for the others we should write a module to do this job.

There is the question as to what to do with the current TANGO_WHATEV_BASE variables, should they override sthing found through cmake find_package, or just be used as hint if find_package fails.

I provided a first draft of what could be done with tangoidl, which is actually a bad example as the project is a single file, but it could be a starting point for discussion.