Allow any server option, random blowfish and recursive path creation

[cgalvarez]

Proposed improvements:

• Allow any server option through the parameter servers (array of hashes, keys being the server property and values the properties values).
• Generate a random blowfish_secret instead of harcoding one in the config.inc.php.erb template.
• Create recursively the provided installation path path (currently the provision fails if any of the involved folders does not exist).