StaticSTSProperties does not allow initialization of crypto from Properties object

This was working in CXF 3.0.7 courtesy of the getProps method which was removed by git commit 40c9bfd, effective for 3.1 branch.

The former possibility to set an initialized Properties object was helpful as an adapter to the spring infrastructure for properties (Resource and Environment abstraction, property placeholder and such) instead of relying on an additional external properties file sourced by cxf-specific mechanisms.