FABRIC-18: Added cache/fabric3-cache extension and linked it to fabric3-spring-library

Conflicts:
	extension/other/cache/pom.xml
FABRIC-18: added slf4j-api jar inside the extension
FABRIC-18: changed ehcache version from latest 2.8.0 to earlier 2.7.5
FABRIC-18: Added fabric3-monitor-log instead of slf4j-api
FABRIC-18: Added a ContributionListener implementation to add sf.net.ehcache import if it is missing
FABRIC-18: Updated a comment