Add alias config to create index endpoint

[jaserud]

Detailed Description

Rollcall can currently only create indices that have entity_centric = alias which tightly couples alias names with index names.

Possible Implementation

• Add alias configuration to create resolvable index request
• check that the alias configuration exists before proceeding with index creation

[jaserud]

this was completed and verified with https://github.com/icgc-argo/roadmap/issues/351