Jeffrey collectors

NOTE: not to be merged yet, just bringing some things to attention.

Most of this is non-client-visible refactoring or additions of new things for the collector API, but there are a handful of things which break backwards-compatibility for users of the Java client (not the API itself).

Many of these I think will be harmless, like changing/removing methods that aren't supposed to be used by clients anyway, but the most egregious one is probably moving the search models into a new package (com.sumologic.client.model -> com.sumologic.client.search.model) which in my opinion is important for organization.

If this change seems too annoying for clients to have to deal with if they upgrade the library, I can revert it. Also let me know if there's anything else in terms of conventions that I should be following.

@weirded @sebastian-mies