Add the use case 44 sequence diagram.
Merge branch 'master' of https://github.com/DataONEorg/sem-prov-design

Conflicts:
	docs/use-cases/images/42_seq.png
Merge branch 'master' of https://github.com/DataONEorg/sem-prov-design

Conflicts:
	docs/use-cases/images/42_seq.png
Tidy up this repo to have better organization for provenance and semantics-specific use cases.  Move the prov use cases into the provenance directory, along with images generated by plantuml.  Leave the plantuml.jar and plantuml.conf files in the parent directory for shared use.