Initial feature for #87

[d-ylee]

Initial feature for Issue #87

Added ability to change physics group in a dataset update Update update_datasets.sql to have optional dataset access type or physics group Fixed HTTP 500 code for DBSPutHandler Added tests for update_datasets with physics_group_name parameter

[d-ylee]

@vkuznet I checked /dbs/prod/global/DBSReader/physicsgroups and saw that some of the physics_group_names have underscores and hyphens. And not all of them are camel case, especially the ones with the underscores and hyphens. Should the regexp also account for these?

[vkuznet]

yes, we need to come up with regexp which covers already existing phys groups.

[d-ylee]

@vkuznet I changed the existing pattern in the static/lexicon_*.json for physics_group.