VIVO-552 Reduce “memory leak” messages at shutdown.

Tomcat also complains if the VALUE of a ThreadLocal is an instance of a class that is defined in the Webapp. So even though the key type was HttpServleetRequest, some of the values were VitroRequest objects. Refactor so the value is the hash code of the request.
VIVO-552 Reduce “memory leak” messages at shutdown.

Back out the changes - locks up on the develop branch.
Merge branch 'maint-rel-1.6' into develop

Conflicts:
	webapp/src/edu/cornell/mannlib/vitro/webapp/freemarker/config/FreemarkerConfigurationImpl.java