Core: Added initializer to preload all drivers

This patch should fix all nasty Thread issues with 'require'
or 'require_relative'. Driver classes are reloaded so there is
not need to call 'require_relative' in thread-not-safe context.
CIMI: Fixed minor test failures
Core: Deltacloud::Library must require models/drivers separately.
Fixed MRI 1.9.3p194 issues