install: enable and upgrade only installed plugins
install: config.ini is now generated, remove old templates
project_default_page.html: unused (cf. templates/default_page.php)
install: remove obsolete install-apache.sh
install: Apache configuration installation and expansion
install: add pear and vendor to include_path
install: tidy httpd.vhosts location
install: tidy etc/
install: move db credentials in post-install
install: plugin httpd configuration installed with the plugin, not with core
install: ditch confusingly obsolete etc/httpd.d/ configs