APP6 Changes (first set)

Changes to tools to support 2 standards (2525 & APP6) and option to
choose
APP6 Changes (set 2)

Primarily changes to Python Tools to support 2 standards
Change to fetch mil template data from github

Get latest data from https://github.com/Esri/military-features-data
Added APP6 Unit Test
Provide better error if styles are not present

Updated readme to reflect new style locations & added better error
messages if styles fail to load
Requested renaming of SIDC to Symbol ID
Merge pull request #13 from csmoore/master

Add APP6 Support (Issue #12)