Add filter clause for BoolQuery

[mvar]

This PR adds filter type support for bool query (Elasticsearch 2.0 feature).

This will allow us to deprecate all filters and implement full "query in filter context" support.

[saimaz]

This is for ES ~2.0 only, need to think how to switch the test cases for ES 1.* and 2.*

[saimaz]

Question is do we need to test this bundle on 1.* at all?

[mvar]

I think at least until next major release we should test on ES 1.* and 2.*. In this case I have added unit test only, so it will run in any environment. We need to discuss more about functional tests.

Don't merge this yet.

[murnieza]

IMHO tests should be executed on both 1.* and 2.* ES vestions.

We can have different test suites and group tests based on which ES versions they should pass.

[mvar]

After discussion with @murnieza about different environments for functional tests we came up with such ideas:

We shouldn't use test suites for different ES versions as it requires to have specific file naming/structure.
PHPUnit has @group annotation. That could be a solution.