split up files in core/ for saner management

core/exceptions.php

@@ -0,0 +1,29 @@
+<?php
+
+/**
+ * Class SCoreException
+ *
+ * A base exception to be caught by the upper levels.
+ */
+class SCoreException extends Exception {}
+
+/**
+ * Class PermissionDeniedException
+ *
+ * A fairly common, generic exception.
+ */
+class PermissionDeniedException extends SCoreException {}
+
+/**
+ * Class ImageDoesNotExist
+ *
+ * This exception is used when an Image cannot be found by ID.
+ *
+ * Example: Image::by_id(-1) returns null
+ */
+class ImageDoesNotExist extends SCoreException {}
+
+/*
+ * For validate_input()
+ */
+class InvalidInput extends SCoreException {}