Give tokens and token exceptions a line and column

[chrisjenkinson]

Token::getPosition() always threw a TypeError because nothing set a position. This implements it and uses the position in the lexer's exceptions:

• Cursor tracks the line and column as it advances, both 1-based, with columns counted in characters. Token takes its TokenPosition in the constructor, and setPosition() is gone.
• NoTokenFoundException and AmbiguousTokenFoundException messages show the line, column and the rest of the line (capped at 100 characters) instead of all the remaining text. The full text is still available through the getters.

Breaking changes: the Token, NoTokenFoundException and AmbiguousTokenFoundException constructors now require a TokenPosition, and guardAgainstWrongNumberOfMatches() takes one too.