Add support for building NSIS setup packages.

Task-number: QBS-16
Task-number: QBS-414

Change-Id: I79eae2a04a238c00e89cdd368230a3a60fedccb7
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>
Reviewed-by: Denis Shienkov <denis.shienkov@gmail.com>
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>