Rename commands and add CLI help

tests/test_rm.sh

@@ -9,6 +9,6 @@ LD_PRELOAD=libasan.so.5 \
 
 $ETCDCTL get --prefix '/vitastor/pg/state'
 
-build/src/vitastor-cli rm --etcd_address $ETCD_URL --pool 1 --inode 1
+build/src/vitastor-cli rm-data --etcd_address $ETCD_URL --pool 1 --inode 1
 
 format_green OK

tests/test_snapshot.sh

@@ -43,7 +43,7 @@ cmp ./testdata/merged.bin ./testdata/check.bin
 
 $ETCDCTL put /vitastor/config/inode/1/3 '{"parent_id":2,"name":"testimg","size":'$((32*1024*1024))'}'
 
-build/src/vitastor-cli snap-rm --etcd_address $ETCD_URL testimg@0
+build/src/vitastor-cli rm --etcd_address $ETCD_URL testimg@0
 
 qemu-img convert -S 4096 -p \
     -f raw "vitastor:etcd_host=127.0.0.1\:$ETCD_PORT/v3:image=testimg" \