gcode: Remove builtin T0/T1/T2/... command support

The builtin Tn command is not sufficiently flexible to control some
multi-extruder printers.  Remove the command and encourage users to
define individual gcode_macros for each Tn instance.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

docs/Config_Changes.md

@@ -6,6 +6,12 @@ All dates in this document are approximate.
 
 # Changes
 
+20191210: The builtin T0, T1, T2, ... commands have been removed.  The
+extruder activate_gcode and deactivate_gcode config options have been
+removed.  If these commands (and scripts) are needed then define
+individual [gcode_macro T0] style macros that call the
+ACTIVATE_EXTRUDER command.
+
 20191210: Support for the M206 command has been removed.  Replace with
 calls to SET_GCODE_OFFSET.  If support for M206 is needed, add a
 [gcode_macro M206] config section that calls SET_GCODE_OFFSET.  (For

docs/G-Codes.md

@@ -9,7 +9,6 @@ Klipper supports the following standard G-Code commands:
 - Move to origin: `G28 [X] [Y] [Z]`
 - Turn off motors: `M18` or `M84`
 - Wait for current moves to finish: `M400`
-- Select tool: `T<index>`
 - Use absolute/relative distances for extrusion: `M82`, `M83`
 - Use absolute/relative coordinates: `G90`, `G91`
 - Set position: `G92 [X<pos>] [Y<pos>] [Z<pos>] [E<pos>]`
@@ -44,7 +43,7 @@ If one requires a less common G-Code command then it may be possible
 to implement it with a custom Klipper gcode_macro (see
 [example-extras.cfg](https://github.com/KevinOConnor/klipper/tree/master/config/example-extras.cfg)
 for details). For example, one might use this to implement: `G12`,
-`G29`, `G30`, `G31`, `M42`, `M80`, `M81`, etc.
+`G29`, `G30`, `G31`, `M42`, `M80`, `M81`, `T1`, etc.
 
 ## G-Code SD card commands