Remove camel case from imageuploadtype in config

This removes the only camel cased option of the config options
**we** added to the config.json.

In auth provider's config parts are a lot of camel cased options
provided. We shouldn't touch them to keep them as similar as
possible to the examples.

Fixes #315

Signed-off-by: Sheogorath <sheogorath@shivering-isles.com>

lib/config/default.js

@@ -53,7 +53,9 @@ module.exports = {
   // document
   documentmaxlength: 100000,
   // image upload setting, available options are imgur/s3/filesystem
-  imageUploadType: 'filesystem',
+  imageuploadtype: 'filesystem',
+  // legacy variable name for imageuploadtype
+  imageUploadType: undefined,
   imgur: {
     clientID: undefined
   },