Ability to work in multi-classloader environments

[reckart]

Is your feature request related to a problem? Please describe.
ClearTK uses Class.forName in various places and also uses an ObjectInputStream which does not allow configuring a custom classloader. This makes it difficult to use ClearTK in environments where there is not only a global application classloader.

Describe the solution you'd like
ClearTK should be able to use the extension classloader of the resource manager of the current UIMA context (may be available via the UimaContextHolder) and also consider the thread context classloader if one is set.