Enable overriding mod-level parameters for apache::mod::passenger

Apache::mod::passenger didn't accept/pass (optional) mod parameters
through to apache::mod, so only auto-generated module parameters were
used. Without this option, apache::mod::passenger could not be used in
conjunction with passenger modules beyond those generated by the OS
package system (in particular, modules compiled via
passenger-install-apache2-module, which uses differing paths). This
commit enables passing in all parameters used with "apache::mod",
documented in the passenger README file.

Modified default RedHat passenger parameters for cleaned-up
installation (prior parameters worked with Apache, but broke
passenger-* utilities, incl. passenger-status & passenger-root).

Updated spec/class tests to verify mod-level parameters; also,
updated RedHat tests to accomodate updated default parameters.

Added spec/acceptance tests for passenger, verifying default
installations for RedHat and Debian systems. RedHat installation test
installs (required) EPEL and http://passenger.stealthymonkeys.com
package repositories.