Add godoc, fix commit hash resolution for submodules

- Add godoc tool (now a separate submodule at cmd/godoc/v0.1.0-deprecated)
- Fix update tool to handle godoc's special tag format
- All tools now use commit hashes instead of version tags

.gitignore

@@ -0,0 +1,16 @@
+# Binaries
+gosetup
+update
+*.exe
+
+# Test binaries
+*.test
+
+# IDE
+.idea/
+.vscode/
+*.swp
+*.swo
+
+# OS
+.DS_Store