integrate plugin hook checking directly when registering

remove plugintester plugin, all functionality now in testdir

--HG--
branch : trunk

py/test/plugin/conftest.py

@@ -1,6 +1,6 @@
 import py
 
-pytest_plugins = "pytester", "plugintester"
+pytest_plugins = "pytester"
 
 def pytest_collect_file(path, parent):
     if path.basename.startswith("pytest_") and path.ext == ".py":