State machine refactoring

[Whitehouse112]

• Removed ValueTable Signal property (obsolete)
• Removed IsSigned Signal property (obsolete)
• Added FSM to parse ValueTable string into dictionary
• Updated Demo application to correctly display ValueTableMap dictionary
• Updated some tests
• Added new tests
• Updated README.md

[Adhara3]

IMHO StringToDictionaryStateMachine would be cleaner with a static bool ParseString() method and a ctor that takes the IDictionary as parameter

public static bool ParseString(string text, out IReadOnlyDictionary<int, string> dictionary)
{
    //State = States.FindingIndex; this goes in the constructor
    dictionary = null;
    var internalDictionary = new Dictionary<int, string>();
    var parser = new StringToDictionaryStateMachine(internalDictionary);
    if(parser.ProcessEvent(text, Events.Start))
    {
          dictionary = internalDictionary;
          return true;
    }
    return false;
}

As another note, I would try to avoid the .Substring calls when not necessary, just keep carrying the current index with you and keep the original text as is without cropping it.

Final note: each method/state is setting a state and then calls a generic method, it could instead call the method directly, that would allow specific signatures an may simplify the state