SERVER-5470 plan cache should be retrieved from database not context
SERVER-11903 Remove BSONElement::validate()

It was mostly used for improving the error messages about BSON that already
failed validation, but it did not cover all validation cases. To replace this
use case validateBSON was enhanced to include the _id of the invalid object in
the error message.
SERVER-12210 no longer put heartbeat message into errmsg field

it now goes in its own 'infoMessage' field
SERVER-12054 Add --sort for mongoexport
SERVER-10564 cache collection scan query plans

Signed-off-by: Matt Kangas <matt.kangas@mongodb.com>
Merge remote-tracking branch 'upstream/master'