Update build & install instructions in README

Per opentechinstitute/commotion-docs/issues/43 and opentechinstitute/commotion-docs/issues/41

Updated build & install instructions at the bottom of the readme. Should now be easier to read. Include instructions on selecting a specific commotion release, router target, or system language. Updates Installation links to point to CCK instead of old redmine wiki.

To test:
1. Read for clarity and typos.
2. Test instructions for accuracy.
3. Check for broken/incorrect links.