Fix replication with animations initialized with `animationTime !== 0`.

If a component implementing `animation.vwf` sets `animationTime` during
initialization, the animation is set to be paused at that time, and
`animationPause$` would receive a reference value based on the current
simulation time. Since `animationPause$` is assigned during
initialization, this isn't marked as a change.

If `animationTime` is set again after initialization, `animationStart$`
and `animationStop$` receive values in relation to `animationPause$`,
and they will be marked as changed. `animationPause$` hasn't changed and
won't be flagged.

But since late joiners initialize with a different simulation time, they
will get a different `animationPause$` value that doesn't work with the
replicated `animationStart$` and `animationStop$` values.

The solution is to always take time == 0 when pausing for the first
time. The absolute time doesn't matter as long as it is correctly
related to the start and stop times.

We should consider holding `kernel.time()` at `0` or making it
`undefined` for a component that is initializing.
Merge pull request #398 from virtual-world-framework/branch/animation-replication

Fix replication with animations initialized with `animationTime !== 0`.