Importing the public libraries caused a name conflict with dart:sky because we
assume people will import dart:sky into a namespace, so I've also changed
skysprites to import dart:sky into a namespace.

I've also removed the top-level description of the Sky package. Instead, we
should host that content on flutter.io.

This might be helpful for #1219.

Also, remove inDebugMode since it's redundant with just using asserts,
which compile entirely out in release mode.

Also, introduce Colors and Typography to hold the material colors and the
typography declarations. Previously we expected clients of these libraries to
import them into a namespace, but that doesn't play nice with re-exporting them
from material.dart.

When we sync() a Component, we need to clear the old Component's _child
pointer, otherwise if we reuse that Component we'll get confused about
what the old child is.

Improve debugging aids for widgets, rendering.

Kill the sky_server on Mac in a way that works to avoid unexpected behavior when working with more than one app at once.

Remove the skyx package

This code is now part of sky_tools.

We need a short name more often than a tree dump, so toString() should
be the short name.

Make debugDumpRenderTree() a global like debugDumpApp(), for
consistency. It's hard to remember the
SkyBinding.instance.dumpRenderTree() incantation.

Fixes #1179.

Adds TexturedLine and animated EffectLine to sprites

We were not removing children if they were more recently synced than we
were. This makes no sense. We should remove all children unless they
were synced this very generation already (in which case they'll be
somewhere else in the tree by now).

We removed this value from the engine because it's not useful.

What's important about this code is that it's presenting services outside the
VM, not the particular technology used to present the services.

This patch is part of a sequence of patches towards fewer top-level libraries.
In this patch, the gesture libraries are combined into one gestures.dart
library.

Conflicts:
	examples/widgets/scale.dart

First pass at support for pinch gestures; panning issues (needs testing)

Conflicts:
	sky/packages/sky/lib/gestures/drag.dart

Conflicts:
	sky/packages/sky/lib/gestures/drag.dart

Factor out GlobalKeyWatcher

- Reorder the methods so they are closer to run order.
- Reindent the code to match style guide.

This also moves the logic that tracks what Widget is being watched into
GlobalKeyWatcher, and much simplifies Mimic based on this.

FlexAlignItems.stretch didn't stretch

Please use GestureDetector instead.

Move Drawer to GestureDetector

This fixes an issue in the stocks app in horizontal mode where you could both
scroll and drag the drawer at the same time.

RenderView has to be a singleton for sanity during tests, otherwise they
all end up in the dirty lists and we end up pumping all of them each frame.

AnimatedContainer isn't an AnimatedComponent.

Turns out it gets nothing out of inheriting from AnimatedComponent.

This widget has no client.

Clarify why we don't assert that ancestor != null.