Improve caching of calledFromClass methods to avoid repeated calls to the classloader for classes not found
Merge branch 'master' of https://github.com/agudian/jenkins-inheritance-plugin into agudian-cache-update
Improve caching of Reflection results.

This is based on the changes from Andreas Gudian.
It improves the previous caching strategy further, to avoid repeated
calls to the classloader (which is a synchronized bottleneck).

It also enables caching of classes that can't be resolved.
Removed permanence of className -> class caching.

Switched to using ConcurrentHashMap's default constructor for increased
parallelism.

Commit is based on comments by Andreas Gudian.
Merge pull request #8 from i-m-c/topic-agudian-cache-update

Improvements to Java reflection caching