Move the auto-importer plugin discovery into the correct place

The script editor should not need to hold a reference to the
auto-importers...

Besides, we are about to use the auto-import feature in the script
interpreter, so we need to hold the reference to the auto-importer
plugins somewhere else...

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Open DefaultAutoImporters for use with the interpreter

The way we do it is to get a completely opaque import generator whose
toString() method generates the import statements.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
DefaultAutoImporters: treat 'JavaScript' as a synonym of 'Javascript'

At least on this developer's MacBook, the language is called 'JavaScript'.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Prepare interpreter pane for more buttons

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Add the 'Auto-import' button to the interpreter

The button is only added for languages supported by the auto-import
feature, of course. And once pressed, it is grayed out.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
InterpreterWindow: add public API to print to the output panel

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Script interpreter: allow to copy text from the output panel

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Script interpreter test drive: add an auto-import example

This makes it substantially easier to test the new feature.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>