Fix Planck and Preonic builds (#5658)

* Planck: Copy contents of Planck rules.mk to each revision

* Planck: Delete Planck rules.mk

* Planck: Concatenate duplicate rules

Concatenate rules that are set and then overridden into one setting.

* Preonic: Copy contents of Preonic rules.mk to each revision

* Preonic: Delete Preonic rules.mk

* Preonic: Concatenate duplicate rules

Concatenate rules that are set and then overridden into one setting.

* Planck: Delete non-specific Bootloader settings from revs. 1 and 2

Deleted BOOTLOADER setting code block, as the checks were only valid for revs. 3-5 and the Planck Light.

Neither Planck rev1 or rev2 set the bootloader via rules.mk, so there's no setting of BOOTLOADER in their rules.mk files.

* Preonic: Fix BOOTLOADER settings code blocks

* Preonic: delete extra blank lines from rules.mk files

* Preonic: delete AVR-type hardware config blocks from rev3

* Update Planck and Preonic readme files

- update Hardware Supported
- update/add Install Examples
- update Docs paragraph

* Enable Bootmagic Lite where it is disabled

Enabled Bootmagic Lite for:

- Planck Light
- Planck revs. 1-5
- Preonic revs. 1 and 2

* Remove `planck_grid` from LAYOUTS rule for all Planck revisions

Community has landed on `ortho_4x12`, which is already set; `planck_grid` is redundant.

1 files changed, 8 insertions, 3 deletions

diff --git a/keyboards/preonic/readme.md b/keyboards/preonic/readme.md
index 5b3c0ec588..85adf635d7 100644
--- a/keyboards/preonic/readme.md
+++ b/keyboards/preonic/readme.md
@@ -6,11 +6,16 @@ Preonic
 A compact 50% (12x5) ortholinear keyboard kit made and sold by OLKB and Massdrop. [More info on qmk.fm](http://qmk.fm/preonic/)
 
 Keyboard Maintainer: [Jack Humbert](https://github.com/jackhumbert)  
-Hardware Supported: Preonic PCB rev1, Teensy 2.0  
+Hardware Supported: Preonic PCB rev1, rev2, rev3  
 Hardware Availability: [OLKB.com](https://olkb.com/preonic/), [Massdrop](https://www.massdrop.com/buy/preonic-mechanical-keyboard?mode=guest_open)
 
 Make example for this keyboard (after setting up your build environment):
 
-    make preonic:default
+    make preonic/rev2: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.
\ No newline at end of file
+Install examples:
+
+    make preonic/rev2:default:dfu         # For Preonic rev1 or rev2
+    make preonic/rev3:default:dfu-util    # For Preonic rev3
+
+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).