CONST_BasePath is split into separate configuration variables
for binaries, libraries and data. These variables as well as
the installation path are now set in the executable directly and
no longer configurable via project settings.
This is the first step towards an installable software. The
executables should know per installation where to find their
necessary data to execute. Project configuration needs to be
restricted to settings that really concern the specific Nominatim
installation.
Executables (including websites) need to be installed in the
build directory, so that they can find the right settings.php.
settings now defines build and source dir.
