Description of problem:

Currently cluster and store use slightly different mechanisms to load their
libraries. 

Store hard-codes its configuration options into the qpidd option set.

No way to load a predefined set of modules without adding command line parameters.

Solution:

Generalized options for loading libraries: 
 --load <lib> load named library.
 --load-dir <dir> load all libraries in dir.

If nothing specified load-dir defaults to a standard location where modules are
installed (e.g. /usr/lib/qpidd/) so that by default all installed libs are loaded.

Library options loaded with libraries: the store modules are hard-coded into the
broker, they should be loaded with the store library. There is already a
mechanism for this, see the cluster code.