WA2 Extensions had two features that have proven more trouble then they
are worth, and so they were removed from WA3 Plugins:
- Virtual methods (methods that automatically invoked super's version
without having to explicitly do that).
- It used to be possible to use strings or tuples to specify parameters
for extensions, and those were automatically "promoted" to Parameter
instances by the metaclass. This feature was never actually used.
This commit cleans up residual code for these features from Plugin
implementations and removes tests that used to exercise them.
- Fixed up some of the signal map for instrumentation
- Changed how priorites are specified -- no longer method name prefixes
but dedicated decorators, including an easy way of specifying a custom
priority level (no longer need to manually connect signals)
- Updated ExecutionTimeInstrument to work with the new system
- Also removed some dead code
Changing the way target descriptions work from a static mapping to
something that is dynamically generated and is extensible via plugins.
Also moving core target implementation stuff under "framework".
