Fix indentation for test-playback-rate
When constructing a new TimedItem, add the item to the parent before updating timing properties

This allows the parent to set the item's start time, which is necessary if the
parent is a SeqGroup.
Fix indentation in test-timing-functions
Add a test for timing functions that map to values outside the range [0, 1]
Make test-timing-functions a little easier to follow
Define types for all properties in css-transitions.
Support integer type
Remove redundant assignment
Support rect() type
Fix line length in test-parent.html
Remove ClonedAnimation
Remove unused house-script.js
TimedItem.parentGroup should be an AnimationGroup, not a TimedItem

TimedItem attempts to use the following methods and properties of its
parentGroup member.
- iterationTime
- paused
- _childrenStateModified()
- type
- remove()
- indexOf()
- _addChild()

Of these, only the first two are provided by TimedItem. The others are added
only by AnimationGroup.
Make use of TimedItem._effectiveParentTime
Make use of ParGroup for DEFAULT_GROUP
Fix demo_example.html

Also replace tabs with spaces and add links as shortcuts to the test functions.
Remove declarative bindings

These were only an experimental work-in-progress, and are likely to change
significantly as a result of the proposed API changes regarding TimeSources.
Removing them now to simplify the process of making those API changes.
Remove templates

These have been dropped from v1 of the spec.
let length interpolation be independent of the expected length types
let length addition be independent of the expected length types