welcome censored data into loadflex

would like to talk with you, @ldecicco, about what the basic loadflex format for censored data should be. we have the option to make it something other than smwrQW, i think, as long as we can translate it into/out of that format for loadReg2 calls.

regardless of the loadflex format, we want to be able to transfer censored data over to EGRET format and therefore need to have a plan for how those data will be formatted in loadflex. this issue is therefore related to #93