Modular inputs update

Another docs pass
Readme updates

For beta
Merge remote-tracking branch 'origin/develop' into feature/MIdocspass

Conflicts:
	SplunkSDK/ModularInputs/Argument.cs
	SplunkSDK/ModularInputs/ConfigurationItemBase.cs
	SplunkSDK/ModularInputs/EventElement.cs
	SplunkSDK/ModularInputs/InputDefinition.cs
	SplunkSDK/ModularInputs/Scheme.cs
	SplunkSDK/ModularInputs/Script.cs
	SplunkSDK/ModularInputs/SystemLogger.cs
	SplunkSDK/ModularInputs/ValidationItems.cs
Merge pull request #28 from splunk/feature/MIdocspass

README and modular inputs API updates