Add configurable query types. Create new simple query string option

[instification]

At present searches are constructed as match queries

However, for various reasons users may wish to incorporate advanced query types such as simple query string

This PR enables configurable search functionality in a backwards compatible way by:

• Creating a new "Query Type" configuration option
  • Defaults to "Match" which is the existing behaviour of collective.elasticsearch
• Creating a new Query type option of "Simple Query String"

The work in this PR can also be extended in future to incorporate many different full text queries

Tasks

• Add query type option
• Add new simple query string option
• Write tests
• Changelog/docs