[Keyboard] Bathroom Epiphanies Frosty Flake rev 20130602 (#15365)

* add optional support for Frosty Flake rev 20130602

* update documentation with instructions on building for rev 20130602

* support revisions using subfolders instead of preprocessor directives

* rules.mk cleanup

keyboards/bpiphany/frosty_flake/20130602/20130602.c

@@ -0,0 +1,24 @@
+#include "frosty_flake.h"
+
+void keyboard_pre_init_kb() {
+    setPinOutput(B7); // num lock
+    writePinHigh(B7);
+    setPinOutput(C5); // caps lock
+    writePinHigh(C7);
+    setPinOutput(C6); // scroll lock
+    writePinHigh(C6);
+
+    keyboard_pre_init_user();
+}
+
+bool led_update_kb(led_t usb_led) {
+    // user requests no further processing
+    if (!led_update_user(usb_led))
+        return true;
+
+    writePin(C5, !usb_led.caps_lock);
+    writePin(B7, !usb_led.num_lock);
+    writePin(C6, !usb_led.scroll_lock);
+
+    return true;
+}