Add support for renaming avatars and make doNotOverwrite=true by default.
Reformat and cleanup code.
While renaming avatars, prevent overwriting existing files.
Enable contao class overwrite feature by removing developers namespace in usage.
Make default fallback image configurable.
Add author and copyright informations.
Merge pull request #4 from tristanlins/master

Rename uploaded files, prevent overwriting of existing files, configurable fallback image and code cleanup