The goal of the refactoring is to support unit tests
for the db library.
For this, a distributed unit test concept has been
introduced (later to be extended to other libs).
Unit tests are shared objects called ".ut" and are
automatically loaded by the ut runner. The bd library
now has two folders - one for sources and one for the
unit tests. The sources are separated into lib and apps.
First unit tests for the writer options have been
provided.