NSIS: Different graphics and cleanups in script

* Defined new headerimage based on BUSMASTER logo text
* Defined new welcomefinishpage based on vertical flyer with twisted arrows.
* Removal of uncommented code from the script.
* Changed tabs to blanks
* Removed blanks at the line endings

Signed-off-by: Tobias Lorenz <tobias.lorenz@etas.com>
Merge branch 'master' of https://github.com/rbei-etas/busmaster