[Data] Avoid persisting duplicates on dictionary import

Avoid attempting to persist objects with
duplicate component ids during data
dictionary import; this resolves some of
the undesired behavior described in
nasa/MCT-Plugins#166.
Merge remote-tracking branch 'victor/mctPlugins166' into iss166
resolve duplicates dictionary import
Merge pull request #168 from JieD/iss166

[Data] Avoid persisting duplicates on dictionary import