Version detection fix

[sbesson]

Reported by @jburel. In the absence of an explicit version key in the rendering file, the detection logic in _getversion() is currently checking the presence of start/end vs min/max keys (as the semantics of these has changed since version 1 and 2) and unconditionally returning 0 (undefined version) in absence of any of these keys. This means a simple rendering file as the following is currently detected as invalid:

---
channels:
  1:
    label: 'DNA' 

ab081ac fixes this issue by returning the version of the latest specification version (2)in this case. 28a10df also increases the type and the range of supported versions when the version argument is present. Several unit tests have been added that should test various YML files and the plugin expectation when loading these.

Travis unit and integration tests should keep passing. Additionally, a simple test should be run with a minimal YML file like the one mentioned above. omero render set should fail without this PR and pass with this PR included.

Proposed relase: 0.6.1

[jburel]

Tested the culprit renderer.yml, no problem noticed this time:

• no version specified

channels:
  1:
    # gray
    color: "808080"

• version specified

version: 2
channels:
  1:
    # gray
    color: "808080"

and

• version specified

version: 1
channels:
  1:
    # gray
    color: "808080"

[sbesson]

i.e. LGTM and released?

[jburel]

Sorry
I wrote another comment but i did not press the button 👍
merging

[sbesson]

Now released as https://pypi.org/project/omero-cli-render/0.6.1/