Improve settings.py

- Load database config from either config.yaml or environment variables
- Mix and match, if you want!
- Move to use logging module rather than just printing stuff
- Error if required database parameters are not required

InvenTree/company/apps.py

@@ -1,12 +1,16 @@
 from __future__ import unicode_literals
 
 import os
+import logging
 
 from django.apps import AppConfig
 from django.db.utils import OperationalError, ProgrammingError
 from django.conf import settings
 
 
+logger = logging.getLogger(__name__)
+
+
 class CompanyConfig(AppConfig):
     name = 'company'
 
@@ -21,7 +25,7 @@ class CompanyConfig(AppConfig):
 
         from .models import Company
 
-        print("InvenTree: Checking Company image thumbnails")
+        logger.debug("Checking Company image thumbnails")
 
         try:
             for company in Company.objects.all():
@@ -30,11 +34,11 @@ class CompanyConfig(AppConfig):
                     loc = os.path.join(settings.MEDIA_ROOT, url)
 
                     if not os.path.exists(loc):
-                        print("InvenTree: Generating thumbnail for Company '{c}'".format(c=company.name))
+                        logger.info("InvenTree: Generating thumbnail for Company '{c}'".format(c=company.name))
                         try:
                             company.image.render_variations(replace=False)
                         except FileNotFoundError:
-                            print("Image file missing")
+                            logger.warning("Image file missing")
                             company.image = None
                             company.save()
         except (OperationalError, ProgrammingError):