Leo won't use Pyzo's file browser without Pyzo itself

[Edward K. Ream]

I have just closed #1095 (stand-alone pyzo file browser) replacing it with #1149 (Improve Leo's file browser).  Recent revs in devel have backed out of today's work, though there is some disabled code that may as well remain.

Today's prototype work showed how to use pyzo's file browser instead of Leo's existing file browser.  This required copying several of pyzo's directories into the leo/external folder.

Everything worked, but it became apparent that there is no real gain to be had.  Opening the browser the first time is quite slow, because much of pyzo has to be inited.  Worse, the pyzo file browser promises features that it can't deliver.  There is no way to remedy this, absent a rewrite of the code. Finally, there is the potential for mischief involving unintended interaction with pyzo's setting machinery.

Instead, it would be much easier, and safer, merely to improve Leo's existing file browser a bit.  See #1149 for details.  This is hardly an urgent project, but it may as well be done for Leo 6.0.

Some of the problems listed above apply to the main pyzo project #1093. But the payoffs for #1093 are much bigger, so handling the (many!) details of interactions between Leo and pyzo seems justified.  #1093 is still a prototype project, but it's still worth almost any amount of work.  This work will surely pay off in some way, regardless of how things ultimately work out.

Edward