Add Tale status to swagger spec/schema

[bodom0015]

Problem

Tale status field is not defined in the Swagger spec, though it is provided in the example value for a Tale.

Approach

Add a definition for the status property to the Tale schema. We should ensure that the attributes required by any clients (UI + worker, at the very least) are defined in the schema in case we ever need to re-generate the code (e.g. when switching frameworks, writing a new client, etc)

Note that even with this change, the Swagger spec produced by /api/v1/describe is not a truly "valid" Swagger spec... see #358 for more details on what would likely be a more controversial set of changes

How to Test

1. Checkout and run this branch locally
2. View https://girder.local.wholetale.org/api/v1/describe
   • You should see the full Swagger spec for this instance of Girder (including the WT and associated plugins) displayed here
3. Search the Swagger spec for Preparing
   • You should see that the status property is now part of the full swagger spec generated by the /api/v1/describe endpoint

[codecov]

Codecov Report

Merging #490 (c40e0d9) into master (4ce464d) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #490   +/-   ##
=======================================
  Coverage   92.78%   92.78%           
=======================================
  Files          52       52           
  Lines        3936     3936           
=======================================
  Hits         3652     3652           
  Misses        284      284           

Impacted Files	Coverage Δ
server/schema/tale.py	100.00% <ø> (ø)

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