: Also minor cleanup and general code modernisation.

Closes #252

See merge request !1407

See merge request !1405

Closes #249

See merge request gaudi/Gaudi!1404

See merge request !1403

See merge request !1395

Gitlab CI authored 2 years ago and Valentin Volkl committed 2 years ago

patch generated by https://gitlab.cern.ch/vavolkl/Gaudi/-/jobs/26119972

See merge request !1402

See merge request gaudi/Gaudi!1380

`DECLARE_COMPONENT_PROPERTY( MyComponent, "myprop", "value" )` can be
used to set properties on already declared components.

See merge request gaudi/Gaudi!1396

Sometimes it is useful to be able to deprecate components, i.e. to
make sure a particular job does not use a certain set of components
(e.g. a multi-threaded job should not use components that are known to
be not thread-safe).

This can now be achieved by setting the "deprecated" property in the
plugin registry:
```
  Registry::instance().addProperty( "MyTool", "deprecated", "optional message" );
```

In addition, the warning can be turned into an error using the new
`setError` method.

See merge request !1400

See merge request !1399

Closes lhcb/Gaudi#3

See merge request !1397

See merge request !1381

Closes #236

See merge request !1398

See merge request gaudi/Gaudi!1394