License switch to LGPL
Summary: Moved from GPL to LGPL with permission to link to other proprietary numerical libraries. Adjusted license notices in all files
Test Plan: unnecessary
Reviewers: pastewka
Reviewed By: pastewka
Subscribers: hu, MartinDoskar, jan.zeman4, rrezakha, gallyamov, afalsafi, maresca, RLeute, richart
Differential Revision: https://c4science.ch/D211