fixed which doc strings are shown for the inspectStats command; moved gui constants into a separate file; hooked up more of the settings tab; built case insensitive cache for the attributes and variable names in the io module; fixed the validator in the gui so it will accept None as well as doubles

git-svn-id: https://svn.ssec.wisc.edu/repos/glance/trunk@189 8a9318a1-56ba-4d59-b755-99d26321be01