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.
WaitOne with timeout is not support in CF
Remove mistakenly added "3"
Internal log for MailTarget is incorrect

When writting the MailTarget settings to the internal log, incorrect
information is written. The reason is that the logging occurs before the
configuration of the SmtpClient.
closes #237
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
Only include ConfigurationManager on supported platforms
Add compiler directive