documentation: rest: improve readability - emph keywords.
Merge pull request #1049 from crate/l/docs-improve-readability

documentation: rest: improve readability - emph keywords.
create predicate documentation for existing predicates
actually execute the examples
refactored match function to predicate
change isAggregate bool to FunctionInfo.Type

in order to also differentiate between Scalar & Predicate
throw proper errors if predicates are used outside WHERE clause
add parser support for multi match predicate
added documentation for new match predicate
implemented support for multi match in ESQueryBuilder
analyze match predicate in its new extended form
add match example results to docs
fix tests for stricter match version
update changes
fixup! update changes