Remove dependency on XDAQ from HcalOnlineDb (for CMSSW_6_2_0_noxdaq)

A compatibility library has been added called xdaq_compat. It includes a
typedef for replacing log4cplus, and copies the toString function from
toolbox.

Most of the changes introduced in this patch are revertible at compile
time by passing the definition "HAVE_XDAQ" to the compiler.

A summary of the changes follows:

* log4cplus/logger has been replaced with an ostream

* toolbox::toString has been copied into xdaq_compat.h

* xgi/Utils.h was unused and so removed