cleanup metadata and add types

[alex-okrushko]

Remove leftover of Reflect
remove a bunch of any types
general cleanup

for #623

@robwormald @brandonroberts @MikeRyanDev Any reason in particular why METADATA_KEY is added to sourceProto.constructor ( aka instance.constructor) instead of simply to the instance?
This prevents me from removing the remaining constructor as any pieces because constructor has type of Function.

I've experimented with putting it just on instance at Firebase and it appears to work just fine, but maybe there is some background that I'm not aware of.

[coveralls]

Coverage increased (+0.007%) to 87.978% when pulling 8b64152 on alex-okrushko:effects-metadata into 55a0488 on ngrx:master.