PageableInMemCollectionBase: Allow modification of empty lists.
PmTableImpl2: fixed some internal names.
FilterAnd: added a static join method
PmUtil: added an isEmpty method for attributes.
Merge remote-tracking branch 'origin/master'

Conflicts:
	pm4j-common/src/main/java/org/pm4j/common/pageable/inmem/PageableInMemCollectionBase.java