fixes #1669 - epel is now a snippet.

This adds another method to install the epel repo, as a snippet,
allowing users to customly change the url, in case that it doesn't fit
their needs or if the url changes again.

to use, simple use:

<%= snippet "epel" %>
when libvirt is not enabled, compute resource provider name is incorrect.
fix error in validation for new compute hosts
fixed useless warning
fixes #1572
fixes #1351 New smart variable and match cannot be entered at same time.
smart vars looks sharper.
[EC2] Adds retry on host not available, add some useful debugging.

- debugging, to get the whole message
- add backtrace to compute resource failure msg
- add debug logging for Fog errors on create
fixes #1670 - Model / OS on "Hosts" page not getting updated properly
fixes #1668 - Paramaters should be text fields.
Send error messages through JSON instead of just {"errors":[]}
fixes #1657 - Support Puppet http reports processor

this patch allow usage of puppet http report processor.
in order to use it simply update your puppet.conf to have the following:

reports   = http
reporturl = http://foreman/reports

NOTE: its not possible to use ssl URLS with the current report processor (AFAIK)
fixes #1650 - Session expiration prevent HTTP authentication delegation
fixes #1619 - X-Forwarded-For multiple IPs
fixes #1648 - User filter on hostgroup could extend to new sub hostgroup.
fixes an incorrect warning about non assigned templates per OS
fixes #1673 - Foreman doesn't work with ruby_parser 2.0.6

Explicitly stating the version of ruby_parser that works with Foreman.
Otherwise you might get:

    superclass mismatch for class Environment (TypeError)
fixes #1656 add support for systems with terabytes of memory
Merge pull request #69 from jmccann/1656-add_TB_support

fixes #1656 add support for systems with terabytes of memory
fixes #1667 - restrcutre fog extensions code