Replace usages of net.sf.ehcache.Cache with org.springframework.cache.Cache

[arteymix]

This will ease the transition to newer version of Hibernate (which eventually deprecated Ehcache altogether) and Ehcache by relying on a generic interface provided by Spring.

• remove runtime creation of caches, everything should be in ehcache.xml and tested at startup in afterPropertiesSet if necessary
• load caches from a generic Spring CacheManager
• make Ehcache a runtime dependency (if necessary)

There are still a few low-level routines from Ehcache that we might want to use in certain contexts. For RDP, I noticed that we would benefit from Cache.removeAll to remove entries in bulk which has no equivalent in Spring Cache.

[arteymix]

With 8be5d33, Gemma is not any longer strictly dependent on Ehcache.