orientdb-1611 Provide lock free version of read cache. Extract interface
orientdb-1611 Provide lock free version of read cache. First implementation of ConcurrentLRUList.
Merge branch 'develop' into concurrent-lru-list-1611
Merge branch '1.7.7' into develop

Conflicts:
	commons/src/main/java/com/orientechnologies/common/io/OFileUtils.java
	core/src/main/java/com/orientechnologies/orient/core/index/OIndexAbstract.java
	tests/src/test/java/com/orientechnologies/orient/test/database/auto/IndexTest.java
Issue #1611 compilation errors were fixed.
Issue #1611 first version of "lock free" LRU list.
Issue #1611 first version of "lock free" LRU list was integrated in disk cache.
Merge branch 'develop' into concurrent-lru-list-1611
Merge remote-tracking branch 'origin/develop' into develop