switch on module in place of switched off module

[xdelaruelle]

When calling switch sub-command it currently unloads specified switched-off module and loads switched-on module after all loaded modules. In version 3 of Modules, switched-on module was set in place of the switched off module.

Depending on usages, this behavior of Modules version 3 may be desired.

To have this behavior operating in a consistent way, every module loaded after switched-off module should be unloaded, then switched-on module should be loaded, then unloaded modules should be loaded again. This way the append-path and prepend-path commands from switched-on module will operate consistently.

This behavior of switch sub-command triggers an automated module handling mechanism, so it should only be triggered if auto_handling configuration is enabled.

Also this should not replace switch sub-command behavior of Modules version 4, so enabling back behavior of version 3 should be done through an option, disabled by default, named switch_inplace for instance.