12.3.8

Issues:

#2048 - IllegalStateException: No query cache enabled on __. Need explicit @Cache(enableQueryCache=true) ... when ebean.disableL2Cache=true l2
#2044 - Using @AttributeOverrides breaking generated SQL (when override nullable and no column name)
#2047 - For #2038 - updated from 12.3.6 to 12.3.7 - NPE BeanDescriptor.findPropertyFromPath(BeanDescriptor.java:1965)
#2041 - Add STI Discrimination on Reference Associations
#2037 - Allow PostCommit transaction callback to recursively add another PostCommit callback bug