Clarify License as being LGPL

[pittfern]

A recent merge #14 that added BrillTransformationRules.js (https://github.com/dariusk/pos-js/blob/master/BrillTransformationRules.js#L5-L16) has introduced code that the header says is GPL, but the license of the project is stated to be LGPL.

This should be clarified.

[Hugo-ter-Doest]

I would prefer to use GPL instead of LGPL because it requires new products that use the module to be GPL as well. I am not the owner of the repository. So I will follow the existing policy, if necessary.

Hugo