Fix labeling bug #342

I have no idea why this works.

Closes #342
Update scatter point emphasis outline for data layer in images

Closes #367
Fix order of axis labels for cubes

Closes #405
Merge pull request #420 from ChrisBeaumont/342

Fix labeling bug
Merge pull request #421 from ChrisBeaumont/367

Fix 367
Add gif to readme
Merge pull request #423 from ChrisBeaumont/docs

gif on readme file
Fix gif
Update video list.

Closes #407
Merge pull request #426 from ChrisBeaumont/docs

Doc update [ci skip]
More thoughtfully clear/restore PV and spectrum annotations on image widget

Closes #417
Closes #386
Merge pull request #422 from ChrisBeaumont/405

Fix axis labels for cubes
Merge pull request #427 from ChrisBeaumont/417

Better treatment of spectrum/pv slice annotations
Show world coordinates at bottom of PV slice

Closes #385
Fix category labels at edge of boundaries

Closes 377
Change qglue return type from data collection to application

Update documentation to demo IPython interaction

Closes #415
Closes #408
Merge pull request #428 from ChrisBeaumont/385

Assorted improvements
Remove image contouring mode

Closes #390
Hide components linked via identity link instead of merging them

Closes #279
Fix snapping behavior in extracted spectrum

Closes #298