Add metadata file.

meta/libraries.json

+{
+    "key": "preprocessor",
+    "name": "Preprocessor",
+    "authors": [
+        "Vesa Karvonen",
+        "Paul Mensonides"
+    ],
+    "description": "Preprocessor metaprogramming tools including repetition and recursion.",
+    "category": [
+        "Preprocessor"
+    ],
+    "maintainers": [
+        "Paul Mensonides <pmenso57 -at- comcast.net>"
+    ]
+}