NEXUS-7298: remove deprecated plugin types (@RepositoryType and RepositoryCustomizer)
[NEXUS-7519] prep: drop recordstore and assetstore
[NEXUS-7519] prep: make assets extensible
[NEXUS-7519] prep: add path as optional asset prop
Merge pull request #835 from sonatype/NEXUS-7519-extensible-assets

[NEXUS-7519] Part 1 of 2: Extensible Assets & Refactoring
temporarily drop rawcontent to ease development
move ComponentEnvelope to model package
use two Entity type params for ComponentEnvelope
add ComponentStore interface
ComponentStoreImpl in progress..