Install script support

A `tools` directory was added to include various support scripts for
installing Payu on Raijin.  Would be nice to phase these out, but they
still seem to be important for managing module files and setting
permissions, etc.

tools/README.rst

@@ -0,0 +1,14 @@
+Support tools and install scripts
+---------------------------------
+
+These are various scripts which aid for installation on Raijin.
+
+- ``nci_install`` is for the newer versions of Payu, which use a fixed Python
+  executable and rely on entry points for command line execution.
+
+- ``legacy_install`` is for older versions, which have less strict install
+  requirements (mostly due to internal bootstrapping techniques which re-apply
+  similar constraint)
+
+- ``get-pip.py`` is a small script available publicly which install pip for
+  Python 2.6.