Add option to visualize metadata with only table names

[csala]

Problem Description

The current metadata can be visualized either showing all the details, including table names, fields and keys, or showing no text at all (each table is just a box).

It would be convenient to have an intermediate format which indicates the name of each table and nothing else.

Expected behavior

The new feature could be accessed as follows:

metadata.visualize(names=True, details=True)   # showing everything. This is the default
metadata.visualize()   # same as the line above
metadata.visualize(names=False)   # shows no names at all, just empty boxes
metadata.visualize(names=False, details=True)  # shows table names, but no details