Libraries for ODB : C++ Object-Relational Mapping (ORM)

The branch contains only two libraries: libodb and libodb-sqlite. 
Other libraries will be added soon.

ODB compiler will be submmited to homebrew-binary.
Can a test be added to do something more substantial than e.g. `--version` or `--help`? See `cmake.rb` for an example of an application formula with a good test and `tinyxml2.rb` for an example of a library formula with a good test. Thanks!