adding extra checks when variable data is loaded to prevent crashing and some cosmetic changes to html report output

added global and variable attributes to report pages; fixed bug in the io module that was causing global attributes to never be loaded; corrected the behavior for purple marking circles behind small numbers of mismatch points and added that behavior to some other kinds of mismatch plots

moving the reports and some other things I missed the first time around to use the new constants module

git-svn-id: https://svn.ssec.wisc.edu/repos/glance/trunk@203 8a9318a1-56ba-4d59-b755-99d26321be01

git-svn-id: https://svn.ssec.wisc.edu/repos/glance/trunk@185 8a9318a1-56ba-4d59-b755-99d26321be01