[#6325] pep8 of app_cfg
[#6325] Moving fixed 'templates' to instance property, update doc

Signed-off-by: Nicholas Bollweg (Nick) <nick.bollweg@gmail.com>
[#6325] using jinja2.TemplateNotFound for bad paths

Signed-off-by: Nicholas Bollweg (Nick) <nick.bollweg@gmail.com>
[#6325] Changing TemplateNotFound Exceptions to match Jinja FSLoader style

Signed-off-by: Nicholas Bollweg (Nick) <nick.bollweg@gmail.com>
[#6325] updated doc to reflect defaults
[#6325] Added tests for PPL, refactored, and fixed issue with partial ordering of EP overrides
[#6325] Fixed errantly removed logger
[#6325] Added correct attribution for toposort

Signed-off-by: Cory Johns <cjohns@slashdotmedia.com>
[#6325] Touched up and tied in documentation for PPL

Signed-off-by: Cory Johns <cjohns@slashdotmedia.com>