Add layout renderer for retrieving values from AppSettings.

+ Supports specifying a default value if one is not found in AppSettings.
Correct extended layout renderer verification test.
Merge pull request #239 from mpareja/app_settings

Add layout renderer for retrieving values from AppSettings.
Fix failing tests
Update project files with new files
Update ProjectFileInfo files
Merge branch 'master' into CodeBetterBuildServer
Fix tests after merge
Only include ConfigurationManager on supported platforms
Merge branch 'master' into CodeBetterBuildServer