Add GRPC server options to meta options for plugins

[zcarlson-signifai]

Implements intelsdi-x/snap-plugin-lib-go issue #43 (Allow grpc Server options to be passed by plugin author).

I took the approach that GRPC server options shouldn't be restricted because restriction can be accomplished later by enforcing (applying) desired restricted options after the user-defined options have been applied.

[PatrykMatyjasek]

Thanks for your contribution.
We are thinking about include your enhancement into examples. It can be done in another PR, but feel free if you want to update this one

[zcarlson-signifai]

I don't think I'm understanding properly -- are you requesting I include my enhancement usage in one of the plugins already present in the examples as well, as a requirement for merge?

[PatrykMatyjasek]

@zcarlson-signifai it will be great if you could update one of existing plugins with your enhancement, but it is not required for merge.

[aasssddd]

I have the same issue as intelsdi-x/snap-plugin-lib-go issue #43
may i ask how to fix this without @zcarlson-signifai's PR?

[tnachen]

Anyone here to merge this patch? Is this library still being maintained?

[zcarlson-signifai]

Is there anything blocking this PR from being merged that I can help with?

[Yajuan-Shi]

GRPC server option can work with this change. Will add option setting in example plugin.