The "dependency" lines really belong to the main port entry, it doesn't
make sense logically to represent them separately and handling them
together will also allow easier dependency management later on. This
commit greatly simplifies the port database parsing to facilitate this,
and removes the -d option from the command line. Instead, ports are
listed with their dependencies, if they have any.
When updating /usr/Ports/AvailablePorts.md, the file or even the entire
/usr/Ports directory might not exist.
To cope with this, we should be able to create it ourselves. To ensure
we are able to do this, we should unveil both /usr and /usr/Ports.
