Keyboard doesn't dismiss when the drawer comes up

When introducing Focus widgets for the Drawer (and ModalRoutes), we weren't
actually giving them the focus. Now we move the focus scope when pushing modal
routes.

Fixes #184

iOS: Make the error message on `flutter ios --init` more descriptive

iOS: Update log prefix for device logs. We don't use SkyShell anymore

Minor update to the message logged when multiple devices are connected with no device ID specified

Example of setting the content type of a POST request

Input asserts while keyboard is dismissed

Now we recreate the stub every time we try to connect to the keyboard. The
underlying message pipe in the stub cannot be re-used, which is why we
previously asserted.

Fixes #776

Avoid launching Xcode after "flutter ios --init"

Add RawKeyboardListener

RawKeyboardListener makes it easier to listen for raw keyboard events.

Fixes #787

flutter start shouldn't log xcodebuild output

Hide EditableString implementation details

Previously, EditableString had many public members because it needed to
implement the KeyboardClient interface. However, that's confusing
because these methods cannot be called directly.

Now EditableString holds a private implementation of the KeyboardClient,
which hides the implementation details.

Fixes #208
Fixes #209

Xcodebuild produces a lot of output that isn't relevant to developers. We
should hide it by default.

improve device notification support

Keyboard service doesn't commit the last edit when it's dismissed

We were getting the proper values, but we thought we were still composing, so
the text was still underlined.

Fixes #115

Support local paths to third-party jars in flutter apk.

Improve error messages for iOS workflow

This reverts commit b240cda8.

We now check that you've got an "ios" directory and that you have the proper
version of Xcode.

Also improve the error message a bit if a download fails.

get a bug fix for multi-line command descriptions

_getPadding was ignoring its argument

Reimplement Inherited.notifyDescendants to use a registration list

...instead of a deep walk.

Add material design features to Input

That way folks can customize it if they want (and it makes the code a
bit more self-documenting).

Now the label animates from its inline position to above the text and
the focus highlight grows into place.