river-options: remove protocol

This protocol involves far too much accidental complexity. The original
motivating use-case was to provide a convenient way to send arbitrary
data to layout clients at runtime in order to avoid layout clients
needing to implement their own IPC and do this over a side-channel.
Instead of implementing a quite complex but still rigid options protocol
and storing this state in the compositor, instead we will simply add
events to the layout protocol to support this use case.

Consider the status quo event sequence:

1. send get_option_handle request (riverctl)
2. roundtrip waiting for first event (riverctl)
3. send set_foo_value request (riverctl)
4. receive set_foo_value request (river)
5. send foo_value event to all current handles (river)
6. receive foo_value event (rivertile)
7. send parameters_changed request (rivertile)
8. receive parameters_changed request (river)
9. send layout_demand (river)

And compare with the event sequence after the proposed change:

1. send set_foo_value request (riverctl)
2. receive set_foo_value request (river)
3. send set_foo_value event (river)
4. send layout_demand (river)

This requires *much* less back and forth between the server and clients
and is clearly much simpler.

doc/riverctl.1.scd

@@ -258,38 +258,6 @@ A complete list may be found in _/usr/include/linux/input-event-codes.h_
 	and is made available through the _XCURSOR_THEME_ and _XCURSOR_SIZE_
 	environment variables.
 
-## OPTIONS
-
-River has various options that are saved in a typed key-value store. It also
-allows users to store arbitrary custom options in the store. Options are
-scoped either globally or per-output if the *-output* flag is passed with the
-name of the output as obtained from the xdg-output protocol. Alternatively,
-the currently focused output may be targeted with the *-focused-output* flag.
-
-*declare-option* _name_ _type_ _value_
-	Declare a new option with the given _type_ and initial _value_. If
-	the option already exists, this command does nothing. The following
-	types are available:
-
-	- _int_: a signed 32-bit integer
-	- _uint_: an unsigned 32-bit integer
-	- _fixed_: a signed 24.8 bit fixed point number
-	- _string_: a string of bytes, may be null
-
-*get-option* [*-output* _output_name_|*-focused-output*] _name_
-	Print the current value of the given option to stdout.
-
-*set-option* [*-output* _output_name_|*-focused-output*] _name_ _value_
-	Set the value of the specified option to _value_.
-
-*unset-option* (*-output* _output_name_|*-focused-output*) _name_
-	Unset the value of the specified option for the given output and
-	cause it to fall back to the global value. Either the *-output* or
-	*-focused-output* flag is required.
-
-*mod-option* [*-output* _output_name_|*-focused-output*] _name_ _value_
-	Add _value_ to the value of the specified option. _value_ can be negative.
-
 # EXAMPLES
 
 Bind bemenu-run to Super+P in normal mode:

doc/rivertile.1.scd

@@ -13,29 +13,6 @@ rivertile - Tiled layout generator for river
 *rivertile* is a layout client for river. It provides a simple tiled layout
 split main/secondary stacks.
 
-# OPTIONS
-
-These options may be set using *riverctl*(1) or another river-options
-wayland client. *rivertile* declares these options on startup, so setting
-these options before starting rivertile requires them to be declared manually.
-
-*main_location* (string, default "top")
-	The location of the main area. Vaild locations are "top", "bottom",
-	"left", and "right".
-
-*main_count* (uint, default 1)
-	The number of main views.
-
-*main_factor* (fixed, default 0.6)
-	The percentage of the layout area reserved for main views. *rivertle*
-	clamps this to the range `[0.1, 0.9]`.
-
-*view_padding* (uint, default 6)
-	Padding around every view in pixels.
-
-*outer_padding* (uint, default 6)
-	Padding around the edge of the layout area in pixels.
-
 # AUTHORS
 
 Maintained by Isaac Freund <ifreund@ifreund.xyz> who is assisted by open