Based on P5's experience

...until people understand them.

To match the Align widget (and several other widgets).

Fixes #6101

These are the last dartdocs needed in the material library.

These let you add Align widget to the inside or outside of a container.
Several customers have asked for these properties.

Fixes #4950

Now past halfway though material.dart by files.

Also, fill out other documentation for these widgets.

Fixes #967

* justifyContent -> mainAxisAlignment
* alignItems -> crossAxisAlignment
* FlexJustifyContent -> MainAxisAlignment
* FlexAlignItems -> CrossAxisAlignment

Fixes #231

The terms "left" and "right" have an LTR bias. Instead, we now use
"leading" and "trailing", for these list and grid decorations so that
we can later rearrange them to match the reading order.

Fixes #2540
Fixes #2548

This patch renames StatelessComponent to StatelessWidget and
StatefulComponent to StatefulWidget.

Fixes #2308

Fixes #1382

Fixes #1278

Fixes https://github.com/flutter/flutter/issues/2369

Previously we used a positional argument for widgets that had multiple
children. Now we use a named argument that defaults to an empty list.

Fixes #241

We need to put the padding on the inside of the list item.

Fixes #1055

A MaterialList understands the sizing, padding, and scrollbar features of
Material Design lists.

Also, add CircleAvatar for showing the circular avatars that are commonly used
in material lists.

The goal is to follow the guidelines in
https://github.com/flutter/engine/blob/master/sky/specs/style-guide.md#packages

Fixes #1638