Use a more unique build directory for RPMs

There a couple of packages that already have directories called "build".
Debhelper uses obj-(arch)-linux-gnu for the build folder, so we can use the
RPM _target_platform macro to do something similar. This directory should
certainly be unique.
do not verify Conflicts and Replaces
Those might not be in the distribution file anymore so they cannot
be checked. They could still be on a user's machine though.
Merge pull request #323 from vrabaud/master

add support for Conflicts and Replaces for .deb
Merge pull request #325 from vrabaud/fix_conflicts

do not verify Conflicts and Replaces
update stdeb.cfg, fix #319
Merge pull request #326 from ros-infrastructure/stdeb_and_319

update stdeb.cfg, fix #319
update stdeb.cfg on more time
changelog
0.5.13
Merge pull request #318 from cottsay/unique-rpm-build-dir

Use a more unique build directory for RPMs
fix blank lines that can appear in the Debian template