SERVER-14831 Add textIndexVersion:1 support to FTSQuery

(cherry picked from commit caa6c9411ba9e3b2b0e9056a0e194009298e4ed8)
SERVER-14831 Fix signed/unsigned comparison in fts_query_test.cpp

(cherry picked from commit b3b6a1a9da2417ce61b2654f9ac5cc2685bc87ad)
Merge remote-tracking branch 'upstream/v2.6' into v2.6