Backlight abstraction and other changes (#439)

* redoes matrix pins, abstracts backlight code for B5,6,7

* slimming down keyboard stuff, backlight breathing implemented

* don't call backlight init when no pin

* cleans up user/kb/quantum calls, keyboard files

* fix pvc atomic

* replaces CHANNEL with correct var in breathing

* removes .hexs, updates readmes, updates template

* cleans-up clueboards, readmes to lowercase

* updates readme

keyboards/sixkeyboard/matrix.c

@@ -40,10 +40,20 @@ static matrix_row_t matrix[MATRIX_ROWS];
 
 __attribute__ ((weak))
 void matrix_init_kb(void) {
+    matrix_init_user();
 }
 
 __attribute__ ((weak))
 void matrix_scan_kb(void) {
+    matrix_scan_user();
+}
+
+__attribute__ ((weak))
+void matrix_init_user(void) {
+}
+
+__attribute__ ((weak))
+void matrix_scan_user(void) {
 }
 
 inline