quota: added function Items

Related to #382.
app: implement Forward function for the createAppQuota action

Related to #382.
app: implement Backward function in the createAppQuota action

Related to #382.
app: declare MinParams in the createAppQuota action

Related to #382.
db: fix index in the Quota collection

I can't believe I'm that stupi.d

Related to #382.
app: drop database on PlatformSuite.TearDownSuite
app: added createAppQuota action to the CreateApp pipeline

Related to #382.
app: delete app quota in the ForceDestroy function

Related to #382.
api: return BadRequest, not BadGateway

Sorry about that.
app: export AppCreationError
app: introduce variable for duplicate apps
app: export Err field in the AppCreationError type
api: return 403 on createApp when user exceeds quota

Related to #382.