Update idea settings

Motivation
----------

The project tree should be clean. And also the team uses JDK 1.8 by
default.

Modification
------------

Ignore some personal plugins, set newer JDK, and resync dependencies
from build.gradle to idea project files.

Result
------

Better IDE defaults shared in the team

Change-Id: I4de4144af971d8160652a9bd9fcff27bc756de8a
Reviewed-on: http://review.couchbase.org/43368
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Reviewed-by: Michael Nitschinger <michael.nitschinger@couchbase.com>