new features: TDBU, TiltPosition, SheerBlackoutDuo

[chrismerck]

TDBU

Top-Down Bottom-Up shades have two rails: a lower rail which opens in the usual bottom-up
fashion, and an upper rail which opens from the top down allowing for privacy while
still allowing light to enter the room.

We use the terms "upper rail" and "lower rail" rather than "top" and "bottom" to avoid
confusion as the meaning of "top-down" and "bottom-up" can be ambiguous.

The TDBU feature requires the Position feature.

Properties

(none)

State Variables

- **upper_rail_position**: (integer) value from 0 to 100: 0 = open, 100 = closed.
- **lower_rail_position**: (integer) value from 0 to 100: 0 = open, 100 = closed.

Actions

- **SetUpperRailPosition(position)**: Set the position of the upper rail.
- **SetLowerRailPosition(position)**: Set the position of the lower rail.

The SetPosition action will set the upper rail to 0% and the lower rail to the
requested position.

Note: if an action requests a position that is not possible due to the
position of the other rail, the Bond Bridge will adjust the other rail
the minimum amount necessary to make the requested position possible.
For example, if the upper rail is at 50% and the lower rail is at 75%,
and the user requests the upper rail to 80%, the lower rail will be
"pushed" to 80% as well.

To change the position of both rails, call both actions in any order.
The start times of the rails motion may be slightly staggered.

TiltPosition

The TiltPosition feature is used to describe a device that can be tilted to a specific position as a percentage,
such as venitian blinds. We currently do not support products that can tilt to an open or closed position
but lack the ability to tilt to a specific position.

Properties

- **min_tilt**: (integer) minimum tilt position (degrees, default 0).
  Traditional wooden blinds can tilt approximately 180 degrees,
  which we model as -90 to 90 degrees, with 0 degrees being horizontal.
  Many motorized blinds can tilt only 90 degrees and are restricted to
  being tilted closed (+90) while in any position other than fully extended.

- **max_tilt**: (integer) maximum tilt position (degrees, default 90).
  Usually unspecified, please default to 90 degrees.

State Variables

- **tilt_position**: (integer) angle of slats in degrees.

Actions

- **SetTiltPosition(position)**: Set slats to specified tilt position in degrees.
- **ToggleTilt()**: Close the slats they are open, open them if they are closed

NOTE: IncreaseTilt, DecreaseTilt, TiltOpen, and TiltClose are not available.

SheerBlackoutDuo

This feature is present on some motorized shades which have two layers of fabric:
a sheer layer and a blackout layer. 

Properties

(none)

State Variables

- **blackout_position**: (integer) value from 0 to 100: 0 = open, 100 = closed.
- **sheer_position**: (integer) value from 0 to 100: 0 = open, 100 = closed.

Actions

- **SetBlackoutPosition(position)**: Set the position of the blackout layer.
- **SetSheerPosition(position)**: Set the position of the sheer layer.

The SetPosition action will set the sheer layer to the requested position and the
blackout layer to 0%. (THIS IS SUBJECT TO CHANGE. If you have a strong preference
please let us know.)

The two layers can often be positioned independently,
but there is sometimes a constraint such as that the blackout layer cannot be positioned
below the sheer layer, or that the sheer layer must be completely extended before the
blackout layer can be extended at all. These constraints are enforced by the Bond Bridge
and need not concern the client. If an impossible position is requested, the Bond Bridge
will adjust the other layer the minimum amount necessary to make the requested position possible.

To change the position of both layers, call both actions in any order.
The start times of the layers' motion may be slightly staggered.