add stats for range_entries
rev_range_entries as well
Merge pull request #331 from Incubaid/stats_update

add stats for range_entries
Merge branch 'incubaid-1.6' into incubaid-1.6-for-1.7

Conflicts:
	src/client/client_main.ml
	src/client/client_protocol.ml
	src/main/main.ml
	src/node/backend.ml
	src/node/statistics.ml
	src/node/sync_backend.ml
	src/node/test_backend.ml