[BISERVER-11486] CDF plugin updates for encoding/decoding/reserved chars...

...	- [cpf-pentaho5] encapsulated parameterProviders.getStringParameter() in new methods within SimpleContentGenerator

	- [cpf-pentaho5] these methods will become a centralized mean of (transparently) URL decoding the paths
	- [all other ctools] content generator classes that extend this SimpleContentGenerator will start calling these methods, instead of parameterProviders.getStringParameter()