add beta version of the query builder

[Loori-R]

Added a UI for the query builder.

• The builder allows creating simple queries based on field names and field values.
• The list of loaded values is cached for improved performance.
• The builder can parse nested queries, such as:

  (foo and foo:bar) or ((foo or bar) and (foo and (foo or bar)))
  

See the list of planned improvements in issue #48.

[dmitryk-dk]

LGTM!

[hagen1778]

Hi @Loori-R!
The builder works for me, but it becomes very laggy when selected field has many options to select.
For example, selecting _msg field staggers my browser for couple of seconds

I think that we should limit the number of options we load into interface.