Make building & installing the core components of OpenSRF optional.

Make building & installing the core components of OpenSRF optional.

For now, this will be of most interest to those interested in installing only
the JavaScript files from OpenSRF. If you disable the core components in
configure, then dependency checking for those core components is skipped and
the JavaScript files will be installed to the desired location.

For example:

./autogen.sh
./configure --prefix=/openils --sysconfdir=/openils/conf --disable-core
sudo make install

... will result in only the OpenSRF JavaScript files being installed in
/openils/lib/javascript/ (although at the moment, the other directories
will still be created).

git-svn-id: svn://svn.open-ils.org/OpenSRF/trunk@1783 9efc2488-bf62-4759-914b-345cdb29e865