Add better documentation of nodes

[bfriesen]

Should be part of the abstract RegexNode class and include:

• General description
• Node-specific behavior
• Success criteria specific to this instance of RegexNode, including:
  • Characters that will match (or not) (for charactor class)
  • Case sensitivity options (for character literal and character class)
  • Dot matching options (for dot)
  • Anchor options (for anchors)
  • Quantifier numbers (for quantifiers)
  • TODO: any other success criteria
• Additional information, if applicable