reduce bgm volume during voice playing
fix doc
add Function Action
fix
tts: Read non-prefs labels.

We want to read yesno_label, for example.
tts: Add self-voicing text to file actions.
tts: Add a new linear focus ordering.

This allows one to navigate through all of the displayables on the
screen with the cursor keys, without having to do 2-d navigation,
which is what Ren'Py does by default.
tts: Allow the user to unfocus all widgets.

This will read out the default text.
tts: Speak bar text immediately.
Document self-voicing, generate doc includes.
sl2: Pass default keyword arguments to the displayable.

This is required so we can pass the layout argument to MultiBox,
which makes the distiniction between fixed, horizontal, and vertical
layouts when the style does not.
Remove spurious code.
Merge pull request #384 from kyouryuukunn/Function

Add Function action, which calls a function with arguments.
Allow RevertableDict to be past as the properties argument to Style.

Fixes #323.
sl2: Migrate grab.
Simplify ScreenDisplayable._hide and make it work with sl2.
Basic framework for profiling screen execution.
sl2: Screen profiling debugging.

This entails writing information about the decisions we make when
creating the displayables comprising the screen.
sl2: Fix debug.
sl2: Encapsulate code analysis into a single object.

This is in preparation for analyzing const/non-const inside a screen.