Allow one to set configuration when using tomcat package.

When tomcat is installed from packages (in EL), the scripts that
are run to launch tomcat do not source setenv.sh, hence the
`tomcat::setenv::entry` resource becomes useless for this specific
case.

In order to still be able to control tomcat instances installed
from package, this PR creates a new resource `tomcat::config::entry`
that does exactly the same thing as `tomcat::setenv::entry` do but for
default configuration file based on the OS.