FMSLogo Code

Update the build to use NSIS 3.0.
This is what someone would naturally install if trying to build FMSLogo today.

Merge in changes from trunk, mostly to get updates to files.cpp

Fix typo: "the play commands starts" -> "the play command starts"

Add missing <userinput> tags to improve readability.

Improve conformance to style guide:
- Use present tense (instead of pluperfect)
- Use upper-case for all Logo procedure names

Fix copy&paste error in explanation of the example using MCI to play an AVI
The "video" was confusingly referred to as "track".

Fix copy&pasted spelling error: asynchornously -> asynchronously

Fix copy&paste error in MCI MIDI example: "video" -> "music"

Replace filenames of "dummy.fil" with "example.txt" in examples.
This improves the readability of the examples.

Refactoring: Extract sendvalue_helper() to remove duplicated logic.