Working joints in sprite physics

These examples haven't been ported to fn3 yet. Before this patch, they caused a
lot of noise in the analyzer output.

Change the default MaterialType to canvas

We changed IconButton to require a ColorFilter to filter the color of the icon.

Canvas is by far the most popular type of material by call site (and makes for
a faster default because it doesn't have a RRect clip).

We can build Fitness again now that playfair has been updated to account for
the package:flutter rename.

Add a bin/flutter.dart to the flutter package

This command will eventually become the main entrypoint for the Flutter tools.
Also, fixup a reference to the "sky" package in sky_tool.

Painting images should not anti-alias (improves performance)

Adds debug drawing for weld joints in sprite physics

Make it fast to draw color icons

Instead of using a ColorFilter, plumb the information down to Icon and thereby
to Image.

...once the animation is done.

Dart supports this properly now.

Add a flag to TextPainter to use ParagraphBuilder

This patch makes it easier to experiment with work on ParagraphBuilder.

MaterialApp assumes that you're using material design.

Also move radial reaction and fix imports for stats box.

Split material design widgets out of widgets.dart

These are now part of material.dart.

Now that you import a top-level file for each layer of the Flutter
framework, within the framework we can use relative paths without being
worried about the copy/pasta problem we used to have.

Also, have dialog buttons use the accent colour.
Also, generally rationalise some of this stuff to match Material better.

Adds support for keeping track of contact points in physics

The root cause was that we crawled the tree to mark anyone who depended
on the updated theme dirty _after_ we crawled it to rebuild it. Thus, if
anyone was already marked dirty when the process started, then got
marked clean by the first (rebuild) walk, then got marked dirty again by
the notification, they'd be clean when they got the notification,
despite already being in the dirty list, which would cause an assertion.

Also IconTheme didn't have an operator==, so it was independently too
aggressive about updates.

Defunct DismissableState should not have live animations