Allow non-String values in environment configuration

Hi there,

while trying to use

I have discovered that

uses

which returns null when the property value is not a string (for whatever reason...).

In my case, this has the effect that using a boolean "true" INDEX_UNINVERTING_ALLOWED is not recognized and an exception is thrown instead as this is now the default. Using a string based

IMHO, this is a pitfall that could be easily avoided by also allowing boolean values.