…sers

Method history extension was using the deprecated mechanism for adding
extension queryCommand: style methods, which can be replaced with the
cleaner declarative association (specified using an annotation) between
extension commands and a query handler.

This is an appropriate time to replace all the queryCommand: switch methods
in the extended dev tools (debugger, class browser, method browser and
package browser) too.

Create a common pattern for the context sensitive commands (browse-it,
inspect-it, accept-it, etc) and provide the majority of this at the
SmalltalkToolShell level. Individual tools implement a mapping function
to return the live selector for the context sensitive command, e.g.
based on subview focus. They then implement the commands to which the
generic/context-sensitive command is matched, and associate these with
query handlers.

A number of bugs and inconsistencies in the enablement/action of the
commands became much more obvious with the new mechanism, and were fixed.

Further refinement of new command querying ClassSelector.

Remove the interim mechanism for declaring additional queryCommand:
methods originally introduced to replace the legacy mechanism. This is
unnecessary as it isn't required for backwards compat (the legacy mechanism
still works), and it is inferior to the individual command query
annotations. The legacy mechanism is now deprecated.