Changes required by List feature.

[scofalik]

This is an overall issue for changes required in engine by List feature. It also covers bugs discovered and fixed during implementing List feature. For complete list of changes look at commits in related PR.
#3603, #3604 and #3675 will be handled in this issue (and related PR), however discussion may be continued in those issues.

[Reinmar]

I reeeeeeeealy miss a list of things which changed. This is a huge PR and no word about its content.

[Reinmar]

OK, shame on me :D I haven't checked the list of issues :D.

[scofalik]

As I said, you can check list of commits, but I'll copy and summarize it here for you...

Changelog:

• Mapper now uses callbacks for position mapping.
• Introduced Mapper#registerViewToModelLength function that takes a view element name and a function that evaluates view element length in the model.
• Introduced RenameOperation, rename change type conversion and default callback for rename change.
• Added: Schema#itemExtends. which enables checking whether item with name A extends item with name B.
• Changed: view.Position#getAncestors changed order of ancestors.
• Added: model.Position#getAncestors.
• Changes in view.Writer: added view.Writer#breakContainer and view.Writer#mergeContainers, renamed view.Writer#breakAt to #breakAttributes and merged it with #breakRange.
• Changed how move and remove change types are dispatched, now they are similar to insert and xxxAttribute change types (have consumable and the changed range is converted item-by-item).

Bug fixes:

• Fixed: In AttributeOperation, 0 as attribute value was treated as no value and caused removing attribute.
• Fixed: view.TreeWalker jumped over range boundary when creating return value.
• Added missing LiveSelection#getLastRange() method, which lack of caused not returning default range when the method was called on empty live selection.
• Multiple doc fixes.