#492 autom. module installation

[Nolens Volens]

the process of installing additional modules is quite
easy but is still open for misconfiguration and errors!

there should be an install_mod.php which uploads the
module.zip and extracts it directly to the propper
directory.
effect:
- the enduser has not to deal with ftp, directories
and so on, just a "select and click"
- the zipped modules are responsible for the correct
naming-convention and location of the needed files
- on any change of the pgv architecture, only
developers and install_mod.php are involved
- integration into the admin page centralizes the
administration of pgv

Christian