[datalogtool] Add datalogtool

This is a support tool for datalog file conversion (and eventually
download/remote datalog file management).

datalogtool/src/main/generate/WPILibVersion.cpp.in

@@ -0,0 +1,7 @@
+/*
+ * Autogenerated file! Do not manually edit this file. This version is regenerated
+ * any time the publish task is run, or when this file is deleted.
+ */
+const char* GetWPILibVersion() {
+  return "${wpilib_version}";
+}