Fix pluginframework build error happening when wrapping is enabled.

This commit fixes the error reported below by adding to the wrapper header
file only the header of classes associated with "wrappable" classes.

Fixes #455

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[ 12%] Built target CTKPluginFramework
[ 12%] Building CXX object Libs/PluginFramework/CMakeFiles/CTKPluginFrameworkPythonQt.dir/generated_cpp/org_commontk_CTKPluginFramework/org_commontk_CTKPluginFramework_init.cpp.o
In file included from /home/jchris/Projects/CTK-build/CTK-build/Libs/PluginFramework/generated_cpp/org_commontk_CTKPluginFramework/org_commontk_CTKPluginFramework_init.cpp:7:0:
/home/jchris/Projects/CTK-build/CTK-build/Libs/PluginFramework/generated_cpp/org_commontk_CTKPluginFramework/org_commontk_CTKPluginFramework.h:17:38: fatal error: ctkConfigurationListener.h: No such file or directory
 #include "ctkConfigurationListener.h"
                                      ^
compilation terminated.
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Merge branch '455-fix-pluginframework-python-wrap-error'

* 455-fix-pluginframework-python-wrap-error:
  Fix pluginframework build error happening when wrapping is enabled.