added ot.string::describe method
quality
added string blank method
quality
added string value method and tests
added string trim method
added aNull method to is object
reduced cyclometric complexity of string.describe
updated string function
added string wrapper method
replaced notblank with string trim method
removed notnull method
refactored assertion name
updated assertion code
removed unused validation parameter
small refactoring
refactored validations/assertions
added class to simplify parameters validation
updated parameters validation
added string.startswith and string.contains methods