updates page titles to be consistent in YAML front matter. Adds templates to...

updates page titles to be consistent in YAML front matter. Adds templates to layout to automatically generate page titles and ids and removed the `# h1` from each page. There is no material difference in the compiled HTML - except it's more consistent, and no visual difference in the browser.

Also makes use of {{slugify}} helper to generate the ids for h1 tags, and the {{default}} helper to DRY up the conditional logic around meta titles and descriptions.