Compare with DB when loading library cache (fixes #256)

src/util/util.cr

@@ -163,3 +163,12 @@ def sanitize_filename(str : String) : String
     .gsub(/[\177\000-\031\\:\*\?\"<>\|]/, "")
   sanitized.size > 0 ? sanitized : random_str
 end
+
+def delete_cache_and_exit(path : String)
+  File.delete path
+  Logger.fatal "Invalid library cache deleted. Mango needs to " \
+               "perform a full reset to recover from this. " \
+               "Pleae restart Mango. This is NOT a bug."
+  Logger.fatal "Exiting"
+  exit 1
+end