gbuild-to-ide improvments

Use gperf instead of ls to find binpath, so that vs2012/3 can be tested
on non-Windows systems.
Output the vcxproj and vcxproj.filters files with indentation and
formatting.
Make some minor changes to improve pep8 compliance.

Change-Id: Ie8ac11ecf75ad170f0756f803c45356685792e5c
Reviewed-on: https://gerrit.libreoffice.org/11797
Tested-by: David Ostrovsky <david@ostrovsky.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>