Refactor the search endpoint to allow for customisation.

[alvinsw]

Changes required to allow user to customise opensearch search query and result:
Extract the codes for building the opensearch search query into an extendable class.
Added queryBuilderClass and queryBuilderOptions to the main Options.

[johnf]

@alvinsw Can you remove dist please?

I'm not convinced we should commit it (although I'm open to discussing it).
Even if we agree, it should be in a separate PR.

Can you expand more on the use case for it?

[alvinsw]

The dist folder is required when we want to add dependency directly from the github repo eg "arocapi": "Language-Research-Technology/arocapi#customsearch". It's in this PR just because other people can test the ldacapi version that uses this branch without having to clone arocapi and do manual npm link.

[johnf]

@alvinsw It makes it very difficult to review with all the dist stuff sitting in there, and I want to make sure we don't accidentally merge it.

Can you please remove from this PR and perhaps create another branch for your use case that includes the dist others can use?
To be honest, it's not super difficult to npm link, which is what I'd typically do if I had this issue.