PR fixes #3545: Allow Leo to import any kind of file on the command line

[edreamleo]

See #3546. Allow Leo to import any number of external (neither .leo, .db, nor .leojs) files from the command line.

This PR refactors and simplifies the code the reads files. This PR should help simplify leoJS.

All plugins and scripts (including Leo's core) should call g.openWithFileName instead of calling methods of the LoadManager class.

This refactoring may have slight impacts on existing scripts and plugins:

Changes to Leo's API

This PR deletes several publicly visible helpers of the LoadManager class.
There is a slight possibility that existing scripts or plugins may be using those deleted helpers.

In all such cases, the fix is to use g.openWithFileName instead.
Leo's core now uses g.openWithFileName to open files of any type.

Changes to the LoadManager class

• Delete lm.openFileByName, an internal helper for lm.loadLocalFile:
• Replace lm.initWrapperLeoFile with lm.openExternalFile:
• Add the fn arg to the the signature of lm.openEmptyLeoFile:

Other changes

• Delete c.createNodeFromExternalFile, another helper for lm.openFileByName.
• Delete a strange Easter Egg involving the k.givenArgs ivar.
  leoVim.py referenced k.givenArgs, but only in disabled code.
• Delete the unused c.wrappedFileName ivar.
• Delete the unused efc.openOutlineByName method.

Tasks

• Retire the --load-type command-line option, adding it to the list of obsolete options.
• Improve error message in load_sessions.
• Fix a pre-existing bug in LM.initWrapperLeoFile: set c.p after creating an @file node.
• Correct the annotation of arguments to LM.loadLocalFile.
• Rename open-outline to open-file (in the menu), retraining the old name for compatibility.
• Remove Easter Egg involving c.k.givenArgs in the open-file logic.
• Make g.openWithFileName the common helper for all open-related logic.
• Set the name of wrapper .leo files to untitled so the wrapper files are not written unless the user agrees.
• Refactor lm.openWithFileName and its helpers.
• Use lm.finishOpen in all helpers of lm.openWithFileName.

[edreamleo]

@tbpassin This PR passes various hand tests. From the leo-editor directory the following works:

leo CONTRIBUTING.md leo/core/leoAst.py leo/core/LeoPyRef.py

[tbpassin]

Note: Now we can see another problem with the --load-type command-line option. The option declares that all files imported from the command line shall be imported the same way (all @edit or @file).

Yes, the old way always bothered me, especially since the Import Any File command already existed.

[tbpassin]

I didn't see anything to remark on. Of course it depends on what loadLocalFile() does, which is apparently hardly changed for the PR, and I'm going to assume it will import non-Leo files according to their file type.

[edreamleo]

@tbpassin Thomas, please review the summary of API changes in the first comment of this PR. Does it look good to you?

[tbpassin]

1. A generalization: g.openWithFileName now uses g.app.gui if the gui kwarg is None
   Will the method still work with a null gui (i.e., the LeoBridge)?

I didn't notice anything else. I can't speak to the completeness of the listed changes, of course. Thanks for addressing backwards compatibility!

[boltex]

Wow ! what a cleanup! :) I'l make sure to bring all those changes to leojs after the alpha launch in one go with all the changes since 6.7.5.

[edreamleo]

@boltex Thanks for your review. The cleanup was long overdue. Glad you approve.