Add support for "combined_fields" query

[vipulg13]

Dear team,

could you please consider adding support to the "combind_fields" query? I could see a similar request is raised in #1512, and a PR #1534 for adding the functionality is still open.

Thanks in advance!

[vipulg13]

is there any tentative date for merging the PR #1557 into the Master? @Telomeraz

[Telomeraz]

@sethmlarson knows it.