Added 'blob' TableSpec column profile, default for binary col types

Added new 'blob' column profile which renders data in hex. All common
binary column types (blob, mediumblob, etc) now use this by default
instead of 'bigtext' which is used by the 'text' column types.

The editor however is still the same (textarea). A hex editor should be
used, but at least now the renderer is better...