DATAUP-188 Add hover states to staging area button, and add margin/letterspacing

[bio-boris]

Description of PR purpose/changes

Add hover states to staging area button, and add margin/letterspacing

Dev Checklist:

• My code follows the guidelines at https://sites.google.com/truss.works/kbasetruss/development
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have run Black and Flake8 on changed Python Code manually or with git precommit (and the travis build passes)

Updating Version and Release Notes (if applicable)

• Version has been bumped for each release
• Release notes have been updated for each release (and during the merge of feature branches)

[coveralls]

Coverage increased (+0.006%) to 16.985% when pulling 0bd8a45 on dataup-188-228 into 20802b5 on truss.

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!

0 Bugs
0 Vulnerabilities (and 0 Security Hotspots to review)
0 Code Smells

No Coverage information
0.0% Duplication