STEP Framework

Instead of locating STEP libraries (lib) through relative paths, the STEP
lib location should be specified using an environment variable, akin to
CATALINA_HOME.
This allows several projects to share the same libraries. It also makes it
easier to keep libraries out of version control repositories.
One disadvantage is that it makes it harder to have different versions of
STEP running in the same machine.

The proposed name for the environment variable is STEP_HOME