4.1.0 - Bugfixes and tracking of key usages in decorated functions

Made some bugfixes related to resources, where creating a resource that had a relative path to the same directory was not working. It was also not possible to create a vault without supplying a resource which it absolutely should be possible to do.

Added new functionality to keys, where the usage of a certain key is logged in the key itself. It only logs usage in functions decorated with vaulter for now, but it can be quite helpful when you need to understand why a key is missing in the vault, or if you just want to know where a certain key is used if you are working on a big project.