Rename String to StringQuoted and Untouched to String

To express "string which will be written to config as provided" user have to write String(). E.g. string 'abc' will be serialized in config to:

example_config_entry = abc

To express "string with double quotes as first and last characters" user have to write StringQuoted(). E.g. string 'abc' will be serialized in config to:

example_config_entry = "abc"

In both cases user in Python code always gets and sets strings without any additional quotation marks. So user writes always

node.config.example = 'abc'

and it is NodeConfig's responsibility to serialize it properly.