Merge pull request #431 from john-hill/PLFM-1896

Plfm 1896
Throw a NotFoundException to avoid potential NPEs
Add getEntityByMd5()
Find by entity by MD5 service and manager wire up
hmm
Fix the controller test error due to null object
Add method getEntityHeaderByMd5()
Wire up getEntityHeaderByMd5() to manager and controller
Merge pull request #435 from eric-wu/develop

PLFM-1472 Find entities by MD5
Force read
Merge pull request #436 from xschildw/conn-leak

Conn leak
removed batching on insert
Merge pull request #437 from john-hill/PLFM-1900

Plfm 1900
Merge branch 'develop' of https://github.com/Sage-Bionetworks/Synapse-Repository-Services into develop