Refactor Query classes

[valencik]

Renames the Query classes to ditch the Q suffix where possible.
When a class name would conflict with a Scala standard library class, like Range or Regex we use the prefix Term resulting in TermRange and TermRegex.
This also helps to indicate that these are term matching queries, as opposed to a boolean combination of queries or a field query.

Additionally we add apply methods to And, Or, and Group, that use varargs for conveniently constructing queries.
Closes #12