document all query dsl features

[trinity-1686a]

our Query language documentation misses a few things:

• phrase prefix queries ( Change syntax of "prefix" queries #4315 )
• wildcard in suffix position ( Change syntax of "prefix" queries #4315 too?)
• exist queries
• range query with >=, <= > and <
• other things I forgot?

[fmassot]

We should probably review the whole page.

[trinity-1686a]

fixed by #4726