added excludes option
add test_exclude_module
update manuals with --excludes command documentation
modified command-line utilities '--excludes' into '--exclude'
and made it repeatable
Merge branch 'options_excludes' of https://github.com/AlessandroMamusa/pyinstaller into issue-1090

Conflicts:
	doc/source/pyi-makespec.rst
Remove useless test.

It's been my fault requesting a test-case for this, because this is
adding a front-end option, while tests currently only cover the
backend.
Remove short option `-e`, keep long option `--exclude`.

IMHO we should be more greedy this using short option names.
Rename option `--exclude` into `--exclude-module`.

This is what has first suggested in #534. Please note, that this
can still be appreviated with `--exclude` or even `--excl`.
Minor clean up: Rename arguments variable `exclude` to `excludes`.
Close #1090: Add option --exclude-module=MODULE.

Also closes #534.