add selector modifiers

[ghostwriter]

This patch adds the following selector modifiers.

• AllOfSelectorModifier (and operator)
• AnyOfSelectorModifier (or operator)
• NoneOfSelectorModifier (not of operator)
• AtLeastCountOfSelectorModifier (at least x of operator)
• AtMostCountOfSelectorModifier (at most x of operator)
• OneOfSelectorModifier (xor operator)

Resolves #186