#727 Fixed failing test
Merge pull request #737 from pshivana/migrate_package_repository_extension

#727 Fixed failing test
Introduced stub package definition service to fixed package_controller_spec and admin pipelines_controller_spec failing. PackageMaterialMetadataLoader modified to listen to plugin change events for GoPlugin class. JsonBasedPackageRepositoryExtension handles empty response for latest modification since call.
Merge pull request #738 from pshivana/migrate_package_repository_extension

Fixing issues with Json based plugin api for package repo.
Change command error stream prefix to STDERR.

Currently output written to stderr by a process shows up in the console
log with the prefix "ERROR: ". This can cause the user to interpret all
messages written to stderr as errors and many are just informational.
This change will help users make this distinction.
Merge pull request #688 from mmb/stderr-output-prefix

Change command error stream prefix to STDERR.