Make flextGLgen.py executable from shell.

Now it can be easily invoked using ./flextGLgen.py.
Get rid of superfluous spaces and newlines for more compact output.
Leave the "do not edit" comment also up to the template.

Might be a bit confusing when looking at the *.template files, but
allows for even more flexibility.
Merge pull request #7 from mosra/minor

Some minor improvements