Updated templates for use by new_project.sh (#3783)

Updated templates for use by new_project.sh (#3783)

* template.h file cleanup

Reformatted the pre-macro comments as block comments.

Updated the ps2avrgb template comment to match the avr template's comment, which was more informative.

Deleted the line about the macro representing the Planck MIT layout, because the macro doesn't represent that layout anymore.

* base template keymap.c refactor

Deleted the deprecated TMK macro functions.

Defined two custom keycodes for use as macros by process_record_user.

process_record_user is now after the keymap and before matrix_init_user, where the deleted TMK functions were.

* Removed an extra " from macro command per @drashna

* Added BOOTLOADER rule to avr/rules.mk per @drashna

* Updated Bootloader sections per @drashna

* Updated links to docs at the bottom of both avr and ps2avrgb template readme.md files

Corrected the links to the Build Environment Setup and the Make Instructions docs.

Added direct link to the QMK Complete Newbs Guide.