Database: allow mysql, config in ini file

Also check for ini file existence at startup

config.py

@@ -2,4 +2,10 @@ from configparser import ConfigParser
 import os
 
 conf = ConfigParser()
-conf.read(os.path.dirname(__file__) + "/fioul.ini")
+ini_file = os.path.dirname(__file__) + "/fioul.ini"
+try:
+    conf.read_file(open(ini_file))
+except FileNotFoundError:
+    print("Configuration file 'fioul.ini' not found")
+    print("Please take a look at 'fioul.ini.example' to create one")
+    exit(42)