Fixed test for the `setup` command

Since version 1.1 the `setup` command must not create the `/etc/setup/setup.ini`
file.
Fixed the `setup` command that must not use the `setup_ini` field
Merge pull request #60 from alquerci/bug/fix_test_pr31

Fixed the cache update for the `setup` command
Moved user config file detection to a dedicated method
Use the program usage of the argparse Python module on a parse error
Moved the `CygAptSetup` instantiation after argv parsing
`parse_rc` now parse all configuration
Clarified the steps on `CygAptMain.main` method