function_score parser throws exception if both functions:[] and single function given

In addition, add a special warning if the misplaced function is a "boost_factor"
function to avoid confusion of "boost" and "boost_function".

closes #5995
Update JNA to latest version

Updating to this version allows to configure a special JNA directory,
in case the /tmp directory is mounted with the noexec option, as JNA
extracts some data and tries to execute parts of it.

Also updated documentation to clarify mlockall and memory settings as well
as pointing to the new jna.tmpdir system property.

Closes #5493
[DOCS] Added Twitter Storehaus client

Added Twitter Storehaus client
Fix behavior on default boost factor for More Like This.

A boost terms factor of 1.0 is not the same as no boosting of terms.
The desired behavior is to deactivate boosting by default. If the user
specifies any value other than 0, then boosting is activated.

Closes #6021