Release 3.15

CHANGES.txt: finalize changes

3.14 release - the "pi" edition

Tag 3.13.1 release

With minor tweaks for windows build

Tag 3.13 release

3.12 release

3.11.13 - bugfix interim release

3.11.12: windows packaging

3.11.11 - windows packaging fixes

3.11.10 release - windows packaing fixes