speed up MXT by checking w/ decompress only every 1 in 200 pages
FastDedup.cpp: added comment
MXT: some optimization for speedup
lime.h: down to 2GB per mem image chunk: get more threads working w/ MXT
MXT.hpp: added comments
zest/src/testcompress.cpp: always decompress check
capture.py: improved sanity checks; verify write permissions for ZEST_MEMIMAGE_PATH
capture.py: default is 3 memory images at 5 minute intervals