Rename .tools to .mystools for Arduino IDE 2 (#688)

* The Arduino IDE considers the .tools directory
 special and warns if it finds .tools the repo
 * Added detection of .tools directory rename
 * Corrected README errata

References #672

.mystools/cppcheck/run.sh

@@ -0,0 +1,19 @@
+#!/bin/bash
+
+# Instantiate the tool runtime shim
+. "$(git mystoolspath).bundle_runtime.sh"
+
+# cppcheck takes one or more files as an argument.
+# --cached or <no arg> for changed
+if [[ $# = 0 ]]; then
+	for file in $(modifiedSourceFiles); do
+		runBundle $file
+	done
+elif [[ $1 = '--cached' ]]; then
+	for file in $(stagedSourceFiles); do
+		runBundle $file
+	done
+else
+	eval "set -- $(git rev-parse --sq --prefix "$GIT_PREFIX" "$@")"
+	runBundle "$@"
+fi