Extend SEE command to bring up Tedit and pdf files

[rmkaplan]

Currently, the SEE Exec command interpets Lisp source files in a useful way, but just shows the characters/bytes for other file formats.

The See menu item in the File browser branches on its recognizable file types (based on what's on the variable FB.SEE.METHODS).

I propose extending the SEE exec command so that it operates in the same way.

[masinter]

thThe "smart" versions sometimes mess up, or fail with ill-formed content or it doesn't guess the file name.

see :hexdump <file>
see :utf-8 <file>
see :tedit <file>

where it bottoms out at @pamoroso 's hexdump.

The filebrowser command menu is very confusing "Fix Directory Dates" under "Recompute"? se