Bug 541517: improved usability of tutorials

- included MinGW install guide
- added brief explanation of actors and link to ROOM concept
- updated some screenshots
- some english language semantics corrected

Change-Id: I78568c23b23397a1deb5e2b3a78dd3049452cefe
Signed-off-by: Hayden Wen <hayden.wen@protos.de>
3 files changed