Fixes trusted players not being allowed when the name has uppercase

I found this bug while testing the plugin. My wife has the name Helelinha1, I added her to the trust list but she was not being able to enter my claim, than I inspected the code and found that the main Flags plugin save the trusted names in lowercase and the BorderPatrol was not changing the name to lowercase, so her name would never be found in the list.

This small change fixes this issue.