LGTM.com-inspired changes:

- Fix: Ensure all apostrophes are escaped for `toXml` utility
- Fix: Avoid error if `URL` is not defined
- Fix (jPicker): Precision argument had not been passed in previously
- Fix (Star extension): Minor: Avoid erring if `inradius` is `NaN`
- Refactoring: Avoid passing unused arguments, setting unused variables,
  and making unnecessary checks; avoid useless call to `createSVGMatrix`
- Linting (LGTM): Add `lgtm.yml` file (still some remaining items flagged
  but hoping for in-code flagging)
- Docs: Contributing file

lgtm.yml

@@ -0,0 +1,7 @@
+extraction:
+  javascript:
+    index:
+      filters:
+        - exclude: "editor/xdomain-svgedit-config-iife.js"
+        - exclude: "svgedit-config-iife.js"
+        - exclude: "dist"