support for various --virt- options for both profile and system, add --power-type to system

We add various --virt options to both profile, and system. We complement
profile by adding a --comment option as it is now supported by all
components of cobbler.
Next we add the following --virt options:

    --virt-auto-boot=VIRT_AUTO_BOOT
        --virt-cpus=VIRT_CPUS
        --virt-file-size=VIRT_FILE_SIZE
        --virt-disk-driver=VIRT_DISK_DRIVER
        --virt-ram=VIRT_RAM
        --virt-type=VIRT_TYPE
        --virt-path=VIRT_PATH

The following option is only add to profile, since in system it's part
of --interfaces:

        --virt-bridge=VIRT_BRIDGE

Finally we also add --power-type to system. To support this option, you
have to install the fence-agents package.

The code is now more streamlined in all modules: We have removed every instance
of defaultto that set the value to '', because this caused puppet to call

     cobbler <subsystem> edit --name=:name --<option>=''
solves #14
added dependency class for managing apache
Fixed typo in documented parameter name

--HG--
branch : jlk/fixed-typo-in-documented-parameter-name-1395868548145
Merged in jlk/puppet-cobbler/jlk/fixed-typo-in-documented-parameter-name-1395868548145 (pull request #23)

Fixed typo in documented parameter name
Merged in igalic/puppet-cobbler (pull request #17)

support for various --virt- options for both profile and system, add --power-type to system
Simple one liner to include the setenvif apache module which is required for the BrowserMatch directive used in the apache configs. From pull req 21.
fixes #16
new options: virt-*, power-type, kernel-options...

and many more!

we add all major virt-options to both, profile and system.
virt-bridge we only explicitly add to profile, providing a default for
systems that use this profile.
Otherwise, system's interfaces already handles virt-bridge!

We also add power-type to system. In order to make use of it, the
fence-agents package is needed.

Finally, we also add the nameservers option to profile, and also add a
nameserver search option.
convert to string before comparison

Everything that could be misinterpreted as a number or anything else is
now converted to string before comparisons
typo: to_ts -> to_s
fix search parameter: previously we reassigned nameservers