Example Plugin: Updating the example plugin for inclusion in builds
Renamed "plugins/exampleplugin" to "plugins/example"

Now consistent with the naming of the other plugins.
Fixed: DENG_API_EXCHANGE requires string.h

The call to memcpy() is done in the macro, so making sure the proper
header is included.
DENG_API_EXCHANGE needs string.h (for memcpy)
Merge branch 'master' into separate-server

Conflicts:
	doomsday/plugins/example/doc/readme.txt