Preliminary work on carrying equipment encumbrance

[heretyk999]

This is the first part part of the implementation of carrying equipment (backpacks, and such) by providing bonus to encumbrance limit (as described in "Carrying equipment", Zweihänder Revised Core Rulebook, p.216).

The PR contains small refactor of the code used for encumbrance, initiative and movement calculations (as the latter two depend on overage), and introduces encumbrance bonus from carrying equipment.

In this version the "capacity"/encumbrance bonus is read from carrying-items.json file, if one is present in the current world. The file should contain mapping of item name to bonus. Example:

{
    "Backpack": 3,
    "Rucksack": 2,
    "Gaff Bag": 1,
    "Shoulder Bag": 1
}

This version of implementation is meant as "internal preview" of the functionality. The second part will follow after agreement on how to provide the bonus data properly (as there are few possible options).

[heretyk999]

After discussion I am dropping these changes for now, as the issue deserves more than a workaround. For now Encumbrance Modifier can be used to handle backpacks.