added installer script

allow passing parameters to install script

removed sudo calls to allow using on systems with no sudo

removed unused variable

install dependencies sed and locate

better discovery of QGISSERVERDIR

allow installing as default vhost

allow selecting the apache version

autodetect apache version
add php to default install
make restarting apache user configurable
Merge pull request #116 from opengisch/add-install-script

Add install script