TranslationManager 17.9.0 release prep

Blocked the Xliff.OM.Netstandard 1.0.2→2.0.1 dependabot bump (breaking major version) via a dependabot ignore rule; closed PR #45
Renamed prerelease.yml's version scheme from {version}-build.N to {version}-prerelease.N
Merged PR #50 "Keep partially-approved jobs checkable while nodes are in progress"; ran two nightly prerelease builds (17.8.3-prerelease.7, .8)
Wrote 4 docs PRs for 17.9.0 against jumoo-docs (memory location fix, glossary user guide, permissions/config toggles, connector-author notes); compressed the 17.9.0 prerelease plan doc from 296 to 85 lines