Improved support for Enterprise Linux family OSs (CentOS, RHEL etc)

* Install pygit from package
* Add Official Salt ZeroMQ 4 COPR repository

Note that Salt itself is assumed to already to be available to the system via yum, via EPEL for example

Remove Duplicates from defaults.yaml and map.jinja

fix empty formulas list in pillar with empty dic.

Fix pillar_roots configuration format in master

This commit fixes how `pillar_roots` are generated and after this fix the
generated configuration does not contain any unnecessary new lines:

```yaml
pillar_roots:
  base:
     /srv/salt/dir1
  dev:
     /srv/salt/dir2
     /srv/salt/dir3
  locale:
     /srv/salt/dir4
```

Before this commit the pillar_roots in `f_defaults.conf` for master would be
generated with a lot of empty lines in between directories, like this:

```yaml
pillar_roots:

  base:

     /srv/salt/dir1

  dev:

     /srv/salt/dir2

     /srv/salt/dir3

  local:

     /srv/salt/dir4

```

The minion configuration is not affected and renders fine.

add pillar_roots for minion and master in pillar.example

Cleanup template for easier user reading

The user will already have it's /etc/salt/minion file, so it doesn't need all this info, and it makes easier to know what has been generated and what not

fixed missing add-apt-repository command when ubuntu is the server one

fixed wrong command name: add-apt-repository became apt-add-repository

ec2/gce profiles/providers are no longer configured if they are not used

Needed because salt-cloud will attempt to load them even if they are
filled with invalid default values, creating error spam.

Added pillar option to redirect profile and map folders.

Change spaces to dashes in IDs for ssh.sls

Exclude require statement when install_packages is False.

The 'require' statement needs a list as input, but doesn't get
any input when install_packages is set to False.

As mentioned in issue #118, provider files may contain passwords
or API keys and should be restricted. Profiles/maps are probably
OK with the defaults.

This obsoletes the salt:cloud:folders and salt:cloud:providers pillar
entries. Provider keys have been moved to /etc/salt/pki/cloud.

These aren't intended to function; they're here to allow the use of
file.recurse on the provider folder, without requiring the user
to provide pillar data for templates they're not using.

Added mine_functions to f_defaults.conf.

Switch config file.recurse to clean by default and tell it to ignore _*

[bugfix] Reverts lookup of salt_cloud_certs to original pillar key, in line with ...

Please refer to issue https://github.com/saltstack-formulas/salt-formula/issues/113.

Fix recursion in api.service

Salt writes it's schedule file to /etc/salt/{minion,master}.d/_schedule.conf

We don't want to stomp all over Salt's files, but we do want a pristine
starting point to lay down our managed config. So we use clean: True on the
file.recurse call, but we tell it to ignore files that start with an _

We have to rename the current config file (_defaults.conf) because it will be
ignored by the rule that ignores Salt's _* config files.

This also means we need to clean up old config files (_defaults.conf) and
restart the service if we cleaned it up.

Add modules to install gitfs backend dependencies

Add modules for gitfs dependencies and documentation for how to use them.

Add setting to not install packages

If you are installing Salt via git/pip, the formula will try to overwrite your
install with packaged versions. This setting makes it possible to avoid that.

Stop using clean: True on /etc/salt/{minion,master}.d

Add note explaining what clean_config_d_dir does and why you shouldn't set it
to True.

New versions of Salt put config files in /etc/salt/{minion,master}.d. We don't
want to erase them by using a clean: True on the file.recurse. This is a
backward incompatible change, but it's necessary to avoid deleting Salt config
files.

Resolves #104

Don't overwrite salt variable

Using a variable named salt is a bad idea when salt already has a variable
named salt.