Disable unused Apache modules

The alias and autoindex module results in /icons/ serving a list of
Apache icons. We don't need this, and so we disable them.

NOTE for future self: If those modules become necessary, then an option
is to override `templates/default/mods/alias.conf.erb` from the apache2
cookbook.
Separate MySQL installation from default
Fix CLI
Fix script
Fix missing conn info
Prompt for MySQL username and password
Don't create users / DBs on non MySQL host
Refactor install script group selection
Generate --help message in main parser
Fix typos and minor errors
Fix typo in attributes generation
MySQL needs to setup the Scalr user
Provide Scalr password in MySQL install done
Make attributes file configurable
MySQL ports should be integers
Group Base -> Group App
Ignore Scalr version when creating Analytics DB
New implementation of the scalr installer
Register the InstallTarget
Don't erase the parser when registering subparsers