Disable serial console by default in 'console'

Also, clean up syntax in 'console' role and prepare it to support
different init systems.
Add 'pattern_prefix' variable in nginx locations

You can use 'pattern_prefix' key in 'location_list' definitions to
specify a prefix for a named location, for example "@service".
Set default locale to en_US.UTF-8 in 'console'
Divert original /etc/issue in 'console' role

This should prevent needless debconf question about changes in
/etc/issue when 'base-packages' package is updated.
Define list of required console packages
Disable locale generation on Travis-CI
Merge pull request #119 from drybjed/role/console

Changes in 'console' role and small 'nginx' fix