edit 8.2.6 version history item.  #4775
add defn of new knob: SENDMAIL  #4764
Merge branch 'V8_2_6-branch' into V8_2-branch
(#4657)  Documentation.
set 8.2.6 release date to Dec 16, 2014
Merge branch 'V8_2_6-branch' into V8_2-branch
reworking DAGMan section, mostly the descriptions of PRE and POST
scripts #4617
Merge branch 'V8_2-branch' into V8_3_2-branch
Merge branch 'V8_3_2-branch'