Symbolize keys to avoid duplicate fields

- Resolves issue reported by @dengwa in https://github.com/cloudfoundry/cloud_controller_ng/pull/274

[#75469572]
Add space quota definition

* add model, controller, migration, and tests

[#74628064]

Signed-off-by: Dave Liebreich <dliebreich@pivotallabs.com>
Add instance_memory_limit to quota_definition api, model, controller

* overlooked in previous commit

[#74629052]

Signed-off-by: Dave Liebreich <dliebreich@pivotallabs.com>
Fix race condition for creating new users

[#75570496]

Signed-off-by: Joseph Palermo <jpalermo@pivotallabs.com>
Ability to assign a space quota to a space

[#74628172]