layers: Add ability to override layer settings from file with a call

Add setLayerOption function call.
diff --git a/layers/layers_config.h b/layers/layers_config.h
index 84cfea6..0010c09 100644
--- a/layers/layers_config.h
+++ b/layers/layers_config.h
@@ -30,6 +30,8 @@
 
 const char *getLayerOption(const char *_option);
 
+void setLayerOption(const char *_option, const char *_val);
+void setLayerOptionEnum(const char *_option, const char *_valEnum);
 #ifdef __cplusplus
 }
 #endif