seg_suffix Requires Explicit File Extension

[srivarra]

If you haven't already, please read through our contributing guidelines before opening your PR

What is the purpose of this PR?

Closes #842. Using file extensions other than .tiff for seg_suffix in the Notebooks: Pixel Clustering, Cell Clustering will not work due to hard-coded in extension types. It should be backwards compatible for now.

How did you implement your changes

seg_suffix used in Notebooks 2,3 will now work appropriately with post_cluster_utils.create_mantis_project and plot_utils.create_mantis_dir.

• seg_suffix now requires the file extension in addition to the suffix.
• Added the constant EXTENSION_TYPES to ark.settings.py which contains file extensions for images, archival formats, and data formats.

Remaining issues

N/A.

[review-notebook-app]

Check out this pull request on 

See visual diffs & provide feedback on Jupyter Notebooks.

---

Powered by ReviewNB

[ngreenwald]

These lines are triggering a change in coveralls on different PRs. In theory we shouldn't ever be generating corrupted feather files, which is why they're variably covered. Can you either exclude them from being counted in coveralls, or generate a corrupted feather file so that the coverage is consistent?

[ngreenwald]

Looks good, see above

[srivarra]

These lines are triggering a change in coveralls on different PRs. In theory we shouldn't ever be generating corrupted feather files, which is why they're variably covered. Can you either exclude them from being counted in coveralls, or generate a corrupted feather file so that the coverage is consistent?

Got it to ignore the (ArrowInvalid, OSError, IOError) lines.

[ngreenwald]

Looks good