CQL::ModifierSet - represents a base string and modifier strings
This class is used as a delegate by both CQLRelation and CQLProxNode - two functionally very separate classes that happen to require similar data structures and functionality.
A ModifierSet consists of a ``base'' string together with a set of zero or more type=value pairs, where both type and value are strings. Types may be null, values may not.
Creates a new modifier set with the specified base.
Returns the base string with which the modifier set was created.
Adds a modifier of the specified type and value to a modifier set.
Returns a modifier with a given type, or null if a modifier of that type isn't present.
Returns a list of modifiers each represented by a 2 element array ref.