Move strdb.* to utility/

Move strdb.* to utility/

These are more similar to the low-level I/O routines already present in
utility (most uses would be easy to replace with TextReader alone, after
some minor extensions), rather than to the other fileio/ stuff.
This, in part, helps breaking the fileio <-> topology cyclic dependency.

Remove unused or duplicate functions or make them private to the source
file.

Convert existing comments to rudimentary Doxygen to avoid warnings.

Change-Id: I3f5262112fabe2bffa16c14c20d987e2e63dcb4f