AMJ60 Refactor (#13530)

* rename LAYOUT to LAYOUT_all

* refactor default keymap

- add license header
- use layer_names enum
- use LAYOUT_all macro
- update keymap to be more generic
- use QMK-native keycode aliases

* info.json: human-friendly formatting

* convert LAYOUT_iso into a proper LAYOUT_60_iso

* LAYOUT_all bugfix

In the physical sense, position k3d is to the left of k3c.

* rework LAYOUT_max into LAYOUT_60_ansi_split_bs_rshift

* remove LAYOUT_iso_splitrshift and iso_split_rshift keymap

* rework LAYOUT_hhkb into LAYOUT_60_hhkb

* amj60.h cleanup

- add license header
- use #pragma once include guard
- concatenate layout block comments
- remove unnecessary function headers

* add license header to amj60.c

* align config.h to QMK template

* align rules.mk to QMK template

* enable Community Layout support

* modernize readme.md

- add PCB image
- convert keyboard data to list
- add flashing and bootloader instructions
- update Docs links

keyboards/amj60/readme.md

@@ -1,14 +1,22 @@
-AMJ60
-===
+# AMJ60
+
+![AMJ60](https://raw.githubusercontent.com/noroadsleft/qmk_images/master/keyboards/amj60/s-l1200_640.jpg)
 
 A 60% keyboard.
 
-Keyboard Maintainer: QMK Community  
-Hardware Supported: AMJ60  
-Hardware Availability: https://geekhack.org/index.php?topic=77636.0  
+* Keyboard Maintainer: [The QMK Community](https://github.com/qmk)
+* Hardware Supported: AMJ60
+* Hardware Availability: [~~Taobao~~](http://item.taobao.com/item.htm?id=43500549469) (no longer available)
+* References: [Geekhack](https://geekhack.org/index.php?topic=77636.0)
 
 Make example for this keyboard (after setting up your build environment):
 
-    make amj60:maximized
+    make amj60:default
 
-See [build environment setup](https://docs.qmk.fm/#/getting_started_build_tools) then the [make instructions](https://docs.qmk.fm/#/getting_started_make_guide) for more information.
+Flashing example for this keyboard:
+
+    make amj60:default:flash
+
+To reset the board into bootloader mode, tap the Reset switch mounted on the bottom side of the PCB.
+
+See the [build environment setup](https://docs.qmk.fm/#/getting_started_build_tools) and the [make instructions](https://docs.qmk.fm/#/getting_started_make_guide) for more information. Brand new to QMK? Start with our [Complete Newbs Guide](https://docs.qmk.fm/#/newbs).