fix: remove circular deps and add ci check

[jelbourn]

Removes the three instances of circular deps and adds a CI check to prevent future regressions.

[jelbourn]

R: @hansl @kara
CC: @mprobst @vikerman

[kara]

LGTM. We should eventually change our system-config.ts to have a main file configured at some point, so we don't have to do @angular2-material/core/core

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