refactoring of node collection db calls

created more ~ 1000 nodes. 
Tested NodesCollectionHandler with: siege -d5 -c3 http://0.0.0.0:8000/api/nodes 
Here is results:
Lifting the server siege...      done.
Transactions:		          98 hits
Availability:		      100.00 %
Elapsed time:		      341.11 secs
Data transferred:	      920.26 MB
Response time:		        7.68 secs
Transaction rate:	        0.29 trans/sec
Throughput:		        2.70 MB/sec
Concurrency:		        2.21
Successful transactions:          98
Failed transactions:	           0
Longest transaction:	       11.37
Shortest transaction:	        4.72