Move IComponentFactory from EntryPoints namespace

[eerhardt]

I chose the same namespace as ComponentCatalog is in, which is the root Microsoft.ML.Runtime namespace. If we ever move ComponentCatalog to a different namespace, we could move this as well.

I spot checked as many places as I could to remove unnecessary using Microsoft.ML.Runtime.EntryPoints statements.

Fix #861

[Ivanidzo4ka]

IArgsComponent [](start = 42, length = 14)

feel free to remove this interface as well. It was temporary introduce for Neural nets entry points almost two years ago, and we no longer need it.

[eerhardt]

I've removed IArgsComponent completely.

[Ivanidzo4ka]

[TomFinley]

This sounds good thank you @eerhardt...

One thing that we will want to consider is your suggestion earlier that we get rid of all these specialized subinterfaces and just make things over IComponentFactory directly. (E.g., no IServerFactory, though there would be one of the appropriate IComponentFactory<... The only thing that seems to practically stand in the way is all these [TlcModule.ComponentKind(...)] declarations -- I'm not sure what they're for but I'd wager they have something to do with entry-points. But I wonder if there's another way we could achieve the same effect. Not related to this, just something that came to mind as I looked at it.

[TomFinley]

Thanks @eerhardt !

[eerhardt]

The existing usages of specialized subinterfaces are all in "Entry Points" APIs. My assumption was that we weren't necessarily working on optimizing these APIs.