Create a unit-test plugin

Move the tcp unit test to the plugin
Add a bihash unit test and a "make test" program to call it
Adjust framework.py to load the plugin, which is disabled by default

Change-Id: Ic229d386a56a9d28dbd54974f231149053ca8f93
Signed-off-by: Dave Barach <dave@barachs.net>
diff --git a/src/configure.ac b/src/configure.ac
index 49beee2..73e5f9a 100644
--- a/src/configure.ac
+++ b/src/configure.ac
@@ -326,6 +326,7 @@
 PLUGIN_ENABLED(stn)
 PLUGIN_ENABLED(tlsmbedtls)
 PLUGIN_ENABLED(tlsopenssl)
+PLUGIN_ENABLED(unittest)
 
 ###############################################################################
 # Dependency checks