scripts/generate-template.sh: Remove obsolete way to update svn repo

The repo is on git now, and there is no need to run that inside the script. So
just remove that param completely.
scripts/generate-template.sh: Exit with error on errors
scripts/generate-template.sh: Don't hide errors

As stdout is used for the file, stderr is used by default for progress
indicators. But if we redirect it to /dev/null we will miss any other errors out
there. We can just run with "-q" (quiet) that hides the progress indicators and
have the errors shown as expected.

So this patch does that: run with -q and don't redirect stderr.
scripts/generate-template.sh: Only fail if the current file does not exist
scripts/generate-template.sh: Optional arguments should be the last arguments

Optional arguments should come after mandatory arguments, if not both end up
being mandatory or ugly "hacks" are needed.
scripts/generate-template.sh: cleanup: Remove trailing spaces
scripts/generate-template.sh: Move mail-reporting logic to a function

This makes the script more readable as a whole.
scripts/generate-template.sh: Add basic documentation
scripts/generate-template.sh: Ignore diff return code
scripts/generate-template.sh: Remove tmp files unconditionally

It may happen that the if is false and it that case the files are not removed.
Just move the rm outside the if, so it's always removed and no garbage is left.
Merge pull request #43 from rata/master

Fixes and improvements to generate templates