Add Validation and rspec tests for $error_log

Without this commit, there is no validation or testing for the
$error_log parameter in the apache::vhost type.

This commit add boolean validation to the apache::vhost type. It also
adds two rspec tests to test the proper function of the parameter.
Merge pull request #186 from trlinkin/refactor_vhost_logformat

Add Validation and rspec tests for $error_log
described the aliases parameter, but does nothing yet
Describe the directories parameter
This should put the aliases in a list after DocumentRoot, provided that .erb can handle hash["key"]
missing hash rocket  => in examples
create a template fragment for directories

...again I hope .erb hash processing works...
Merge branch 'vhost_alias' into all_features