docs: Improve home page

docs: Improve home page

Organize CSS and Javascript files into directories, separating vendor
source code from home-grown.

Separate new properties and selectors in Bootstrap CSS (already edited
for Hugo) from:
1. Original property values; and
2. Changed property values.

For the home page:

1. Clarify the English text;
2. Add some element names to classes in CSS selectors (to speed loading);
3. Document the Owl Carousel and Highlight.js versions;
4. Add Owl Carousel's license;
5. Restore HTML comments to browser source views;
6. Make the beginning GitHub button transparent on focus (like the others);

7. For the final, colored Twitter and Github buttons:
  a. Remove the dotted box on focus; and
  b. Color them green on active.

8. To increase (layout/) source readability:
  a. Place `class` attributes before `href` attributes;
  b. In `class` attributes, place more-specific class names before
     less-specific; and
  c. Comment the beginnings and ends of Bootstrap rows.

9. To increase understandability during development:
  a. Document the meaning of CSS file, `HPstyles` by renaming it to
     `home-page-style`;
  b. Move inline styling to CSS stylesheets;
  c. Separate @media queries to a file;
  d. Separate the inline Owl Carousel custom Javascript to a file;
  e. Use regular Owl Carousel CSS files instead of minified ones; and
  f. Rename the wide, landscape desk background image filename from
     `desk-long` to `desk-wide`.