Plugin configuration happens now in CMakeLists.txt files in corresponding plugin directories.

plugins.cmake now contains REGISTER_PLUGIN_FUNCTION which accepts the following parameters:
  - TARGET: the name of the plugin (dynamic plugins will be named ${TARGET}.so (or .dll)
  - SOURCES: source files
  - LIBRARIES: additional libraries for linking
  - INCLUDES: include directories
  - CONFIGURATIONS: possible plugin configurations: valid arguments are DYNAMIC, STATIC, OFF
  - DEFAULT: default configuration (see CONFIGURATIONS)
  - COMPILE_OPTIONS: compiler flags

The default plugin configuration can be specified via cmake parameter -DCLIENT_PLUGIN_${TARGET}=[DYNAMIC|STATIC|OFF]