Externals Update, master branch (2020.10.19.)

Updated all projects to atlasexternals-2.0.82. The changes wrt. atlasexternals-2.0.81 are (atlasexternals@2.0.81...2.0.82):

• Added histgrinder 0.1.2 as a new external in PyModules;
• Added Findstomppy.cmake to AtlasLCG.

Both of these are needed by the DQ code, with some high urgency as I learned from @ponyisi.