New plugins symlinks

[prioux]

This is a significant improvement in the way plugins are integrated.

The structure of the "installed_plugins" folder was
changed slightly to flatten the subfolder for userfiles.

Previously, we had something like:

installed-plugins/userfiles/text_file/text_files.rb -> (plugin_loc)

and now we have:

installed-plugins/userfiles/text_file.rb -> (plugin_loc)

This means the boot code for the Rails app no longer globs
into a large set of folders to find its Ruby code files, speeding
it up.

But it also means I had to create a new "views" section
to hold the symlinks to the userfiles's "views" subfolders.

The rake task to installed and cleanup the links has been
adjusted, you WILL need to run 'rake cbrain:plugins:install:all'
to adjust all the symlinks. (And even maybe :clean:all first).

The helper method that builds the userfile view paths has also
been updated.

Fixes #816

[MontrealSergiy]

It might increase risk of file name intersection among different types?

[prioux]

Not really. Since the file names (e.g. xyz.rb) are for Ruby classes, and there can only be one Ruby class of name "Xyz", there can't be two "xyz.rb" files anyway anywhere within the system.

[prioux]

I found a few problems with this as I am testing some more. Hang on.

[prioux]

So this has been tested on a production server (!) that was idle, and it seems to be right.

One happy consequence of the change is that in development mode, the Rails app won't load any of the model file until it's actually needed by a Ruby statement. You can test it in a console (in dev mode) with a statement like this:

in_memory = Userfile.descendants.map(&:to_s)

This will show the models currenly loaded; those were loaded most likely because a database table refer to them.

Pick a Userfile subclass that is not listed but you know exist (e.g. XMLFile) and just type the class name in the console:

XMLFile
 => XMLFile id: integer, name: string, size: decimal, user_id: integer, ...

Then if you run the "in_memory" statement again, you should see the class has been added to the list.