Query builder API

[Frando]

Discuss the API added in #1:

Especially:

• When do functions return this, when do they return a plain object? The term method returns a plain object, and this is used within the bool query - however, coudn't a term query also standalone?
• How will the searchquerybuilder relate to other queries?
• SearchQueryBuilder is a bit long of a name

[hng]

In general I am still unsure what the way is to create a dsl style query api with javascript. I think the term part is only used inside a bool query.