Version 0.993
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* Allow plotwt, plotbp and plotapd to send params though command line
* Move difxsniff from calcif2 into this module
* Change to not allow/require png support; pgplot is broken w/r/t modern versions of libpng

Version 0.992
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* Post DiFX-2.2 / DiFX-2.3

Version 0.991
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* 20120912: Craig updated plotbp to make a second zoomed-in plot if the dynamic range caused by RFI or other strong lines was too high.
* Version for DiFX-2.2