start reorganizing docs, write more docs, shift plugin docs, to proper documentation,

use sphinx, remove old docs ... work in progress.

--HG--
branch : trunk

example/funcarg/test_simpleprovider.py

@@ -0,0 +1,7 @@
+# ./test_simpleprovider.py
+def pytest_funcarg__myfuncarg(request):
+    return 42
+
+def test_function(myfuncarg):
+    assert myfuncarg == 17
+