Create composite limit

[ibboard]

Some ​recent discussions highlighted the fact that we might need composite limits (e.g. for equipment) where the limit is a combination of two other limits.

The known use case is where a unit can have one and only one of a certain class of weapon if they are between 5 and 10 models. The "if >= 5" can be handled by a ratio limit of 0.2 rounding down, but that allows 2 for a unit of 10, so we need to combine it with "and an absolute limit of 1".

[ibboard]

​IBBoard:#45 is complete, so we can now make use of them.

[ibboard]

(In r585) Re #279: Create composite limit

• Change uses of "AbstractLimit" to "ILimit" as composites don't have a number themselves and can't extend AbstractLimit
• Refactor limit parsing code out into a separate class
• Use grouping to allow for re-use of limit types in schema
• Add min and max composite limits in schema

[ibboard]

(In r586) Re #279: Create composite limit

• Add first tests for limit parser - composites are parsed, but children aren't picked up by XPath query yet

[ibboard]

(In r587) Re #279: Create composite limit

• Ignore XPath and go for all child nodes, since we want to warn in future if an unsupported limit is ignored
• Make the "any" option in the limit choice group a singular instead of 0+ to ensure we get a choice when we use the group

[ibboard]

(In r588) Re #279: Create composite limit

• Create separate tests for min and max limits (rename existing test data file)
• Fix namespacing of limit nodes
• Add test for nesting of composite limits
• Add tests for empty composite causing failure

[ibboard]

Fixed in r588

[ibboard]

Retro-actively tag RC1 releases as released