(dsl): Support 'matchPhrase' query

[drmarjanovic]

Description:

Resolves matchPhraseQuery in #91

• Provided matchPhrase query.
• Provided boost options both for match and matchPhrase queries.
• Addressed warning for the example app.
• Improved documentation (provided .).
• Changed the way of constructing fields in paramsToJson methods.
• Adapted existing and provided new tests.
• Provided structure for the website.

[arnoldlacko]

Why do we need to delete everything if we're recreating the index between each test?

[arnoldlacko]

Does this result in a structure like:

{
   errors: {
      body: [
         "This is an error"
      ]
   }
}

?
Can we simplify that and also avoid naming a class with Data?