Lazy managers

[pett]

Would like the ability to start a manager later than ChimeraX startup, for managers that are not used often. For example, the Build Structure tool has various ways of starting a structure (single atom, PubChem ID, SMILES string, etc.) that I want to be extensible through the manager/provider mechanism, but would prefer not to have the Build Structure module executed every time ChimeraX starts simply because the module has a manager.

This implies that the Toolshed needs to support lazy managers. Also, notifying managers about new providers from newly loaded bundles was overlooked, and therefore the BundleAPI needs a find_manager() method so that the Toolshed can find the manager to notify.

[Greg Couch]

Notifying managers from newly loaded bundles was done by Eric. Unclear if lazy managers are worth the work. A bundle's init.py can be structure so no additional modules are imported and minimize the overhead.

[pett]

It's fine that you assigned it to me -- I intended to implement it myself now that I've worked with the toolshed code a little and understand it somewhat.

Importing nothing else in a managers init.py is frequently awkward/ugly because that's where the bundle's public API is, and where the manager will want to put classes and functions that providers need to use.

[pett]

A manager with the attribute autostart="false" is lazy.