Multiple changes in the plugin build infra

- configure.ac - some plugins are enabled by default
- Plugin .so files are placed into corresponding subdirs
- WITH_PLUGIN_TOOLKIT macro is retired - not needed anymore
- plugins/build-data is removed
- plugin makefiles are not building static libs anymore
- plugin makefiles are not installing header files to /usr/include
  anymore

Change-Id: I55681bd9ce34811f7eb1b2b24d9f0ca42df1cf04
Signed-off-by: Damjan Marion <damarion@cisco.com>
diff --git a/build-data/platforms/vpp.mk b/build-data/platforms/vpp.mk
index 45f74d3..fb1867c 100644
--- a/build-data/platforms/vpp.mk
+++ b/build-data/platforms/vpp.mk
@@ -38,9 +38,7 @@
 # Set these parameters carefully. The vlib_buffer_t is 128 bytes, i.e.
 vlib_configure_args_vpp = --with-pre-data=128
 
-# Enable plugins here, and no place else, via multiple --enable-XXX-plugin
-# stanzas.
-plugins_configure_args_vpp = --with-dpdk --enable-sixrd-plugin 
+plugins_configure_args_vpp = --with-dpdk
 
 # DPDK configuration parameters
 # vpp_uses_external_dpdk = yes