new icons for linux, etc.

- new xpm resources for different linux window managers
- new png files for autoresizing on different linux window managers
- favicon with new logo
- window .ico with new logo
- updated debian package script
- updated changelog
Merge pull request #2650 from jonasschnelli/new_xpm_icons

new resources for linux software package managers
Docs Markdown Cleanup
Merge pull request #2666 from super3/master

Doc Cleanup with Markdown
Merge branch 'master' into Qt5