Multiple changes here:
- annotation unpacking is smarter and if it only needs runtime
  retention annotations it uses reflection and doesn't unpack the
  bytes to discover class level retention annotations.
- Reflection worlds are shared if for the same classloader.

If there are problems at weave time the weaver may attempt to
disassemble some code to produce a nice error message. Until this
change that disassembly code did not understand invokedynamic.
This would make it fail to disassemble and instead of seeing the
real problem you see a disassembly problem. With this fix we
should now see the underlying problem in the issue.

Issue: #525541

- reduced build level from 8 to 7 so that the weaver can be used on Java7.
- minor readme tweaks

If an anonymous class calls a method ITD'd onto one of its own
supertypes (e.g. new A() { xx(null); }) then it can be reported
as an ambiguous method invocation on Java8. There is different
handling for Java8 that is revealing an issue. The intertype
method declarations are recorded in a member finder attached to the
target type (A in this case). When the local type binding is
built it gets all the methods from supertypes added to it - this
unfortunately includes the ITD method.  Then later when something
asks for all 'xx' methods on A, it finds the ITD method from when
A was constructed and an additional copy from the member finder.

The quick fix is for the member finder to use a set rather than
list when answering 'what are the xx methods'. If this proves
a problem down the line the deeper fix would be to avoid including
ITDs when the local type binding is built.

In writing a testcase for 352389 I discovered overweaving
just wasn't working for a compile time series of test steps.
This was due to a guard preventing secondary calls to
addOrReplaceAspect. Without the secondary call the crosscutting
collector for the aspect had recorded no mungers from the
original aspect because it was still using an EclipseSourceType
delegate. Later when it was using the binary BcelObjectType
delegate and mungers were available, they weren't collected
because of that missing addOrReplaceAspect call.