Clean-up hash lookup and avoid local undef var
allow disabling default vhosts under 2.4

when disabling the default vhost(s) under 2.4, there's nothing to
include in $sites-enabled/, which causes the following error:

    The apache2 configtest failed.
    Output of config test was:
    apache2: Syntax error on line 46 of /etc/apache2/apache2.conf: No
    matches for the wildcard '*' in '/etc/apache2/sites-enabled', failing
    (use IncludeOptional if required)
    Action 'configtest' failed.
    The Apache error log may have more information.

by using IncludeOptional (as recommended), we allow the use of httpd as
simple web server, with single purpose configuration, without having to
define a (default) vhost.
Support parameters along with proxy_pass
Support keywords along with proxy_pass, use hash for params
Add some tests for ProxyPass parameters
Linting and adding some tests

Adding tests
MODULES-1446: mod_version is now builtin

while we are not loading it (by default), we should make it easier for
people transitioning their configuration from 2.2 to 2.4 to find issues:
thus adding a warning when someone tries to load mod_version.

---

things i have learned during this pr:

× @hunner: There is no '&&' in puppet; only 'and'*

× add puppet to PATH, so vim can check syntax. thanks @mhaskel
especially for the patience.

*zuhl.
Merge pull request #909 from igalic/no_default_vh_24

allow disabling default vhosts under 2.4
Merge pull request #908 from igalic/mod_ver

MODULES-1446: mod_version is now builtin
Merge pull request #841 from PierreR/patch-1

Clean-up hash lookup and avoid local undef var
Merge pull request #914 from tfhartmann/tfhartmann_proxy_pass

Support parameters along with proxy_pass now w/ tests