Force the file extension to lower case
Add a config var to let the choice of having the lower case on the extensions when uploading.
The default value is set to FALSE.
New var name to make it more comprehensive
Changes to follow the styleguide, proposed by narfbg (thanks to him)
Fix #2498
Update library documentation and changelog
Merge pull request #2497 from yazuu/upload

Upload : change the file extension to lower case
Issue #2508