Various fixes - links, calendar updates, background images

- Put links in home page navigation, subpage navigation, and footer.
External links open in new tab. The links won’t work until the site
resides on its own root directory.
- Style changes to the calendar
- Optimized background images and stored raw images in a new folder
(can be deleted later if we decide the optimization level is sufficient)
- Background images now fade in on page load (home page only to keep
the effect from getting old).
- Background images now randomly selected on every home page load, and
sessions keep the background the same for any subpage visits.
- Removed unused font weights to decrease page load time
- Trying out a new minifier, updated .gitignore to exclude them from
committed changes until I know how to use it
- Forgot a semicolon