Add support for default values to processors.
Update PlistReader to use new input variables defaults.
Move default value processing into existing for loop.
Update FileFinder, URLTextSearcher, and Versioner to use new default values ability.
Add debugging output for applying default values.
Merge branch 'master' of https://github.com/autopkg/autopkg into PlistReader-default-keys

Conflicts:
	Code/autopkglib/FileFinder.py
	Code/autopkglib/PlistReader.py
	Code/autopkglib/URLTextSearcher.py
	Code/autopkglib/Versioner.py
	Code/autopkglib/__init__.py
Merge remote-tracking branch 'origin/pr/107'
Initial support for verifying requirements