adding support for correcting AWIPS data type distortion on load; note this isn't yet hooked up to the outer methods in compare

git-svn-id: https://svn.ssec.wisc.edu/repos/glance/trunk@209 8a9318a1-56ba-4d59-b755-99d26321be01

git-svn-id: https://svn.ssec.wisc.edu/repos/glance/trunk@204 8a9318a1-56ba-4d59-b755-99d26321be01

moving a huge pile of strings into constants modules and refactoring several groups of functions out of compare.py into different modules organized by their logical function

git-svn-id: https://svn.ssec.wisc.edu/repos/glance/trunk@201 8a9318a1-56ba-4d59-b755-99d26321be01