At the moment KDE ports use bsd.kde4.mk to handle their dependencies. When working on the ports for KDE Frameworks and Plasma5 it seemed to be more reasonable to create a new kde.mk instead of adding an bsd.kde5.mk.
The kde.mk in this review is a stripped down version of the one we are using in the KDE Test repositories plasma5 branch  to only contain the parts relevant to the current KDE4 ports in the portstree .
Changes to the KDE Ports needed by this:
- Replace USE_KDE4 by USE_KDE 
- Add USES=kde:4 
 The version in the plasma5 branch also handles frameworks/plasma5 and handles MASTER_SITES via a KDE_DIST variable similar to bsd.qt.mk for Qt Ports -- I chose to leave this out for now, as the diff is already large enough.
 I chose USE_KDE instead of USE_KDE4, USE_KDE5, USE_KDEX as the version we want is already specified as argument to kde:<arg>
 For KDE Frameworks and Plasma5 ports this would be kde:5