Changed `site.html_pages` to `pages_list`, to repeat the nav order of the grandchildren in the nav panel.

Co-Authored-By: Patrick Marsceill <pmarsceill@users.noreply.github.com>

Added a configuration option to determine whether the sort order is case-sensitive.
The default is case-insensitive.

To test:
- open `/just-the-docs/docs/utilities/` in the browser,
  and check that the navigation links in `Utilities` are sorted alphabetically;
- in `docs/utilities/layout.md', change the preamble to `title: layout`,
  and check that the  links in `Utilities` are still sorted alphabetically;
- add `nav_sort: case_sensitive` in the configuration file,
  and check that the link to `layout` is now listed last under `Utilities`.

Co-Authored-By: Patrick Marsceill <pmarsceill@users.noreply.github.com>

Currently just-the-docs renders two title and description tags
when used with jekyll-seo-tag. This patch fixes plugin detection
conditonal.

It appears nav_exclude only works on top level navigation items. I needed it to work at the child level as well. I believe these changes accomplish that for the child and grand_child levels.

Love this theme. I've used it a few times. Apologies if this pull request is not according to convention. This is the first time I've done it on someone else's code. Thanks!

- Introduced "ga_tracking_anonymize_ip" parameter to enable/disable Google Analytics IP anonymization (to comply with GDPR).

(cherry picked from commit ce530f36fa0549c78ffe53ea6077f44f6f0b330f) (+1 squashed commit)
Squashed commits:
[69b7718] - enable GA anonymize_ip

(cherry picked from commit f2b67c632af72b61dd634b9a337200781519691e)

This commit resolves #207.

When `nav_order` is omitted, the order of nodes at each menu level (and in the auto-generated TOC) is alphabetical by `title`, instead of random.
Any nodes with a specified `nav_order` precede all nodes at that level where it is omitted.
Note that `nav_order` fields must have a uniform site-ide type: integers and strings cannot be mixed, otherwise Jekyll reports errors.
The implementation filters the ordered and unordered pages from `site.html_pages`, sorts them separately, and concatenates the resulting arrays.

This reverts commit 7220197a.

Mathjax config options added.
`compress_html` config option changed,
Mathjax script loaded by head when `page.mathjax` is truthy.
Documentation and test page added.
See also issue #198.

This reverts commit 0cfc0f03.

This reverts commit 8ac545a5.

This reverts commit c282e4b0.

This reverts commit 5d58a663.

This reverts commit 89f79138.

This reverts commit 209ac7be.

Restrict navigation to display only direct children.

This reverts commit 8ac545a5.

This reverts commit c282e4b0.

Separating new PR from #188, since indpendent.

The current default is that when a grandparent is selected, the links to its
children *and all its grandchildren* are displayed in the navigation menu.
Setting `grandchildren_branch: true` in `_config.yml` delays the display of links
to grandchildren until their parent is selected.

Automatically replaces the title with a logo

A `navigation-list-child-list` is not displayed unless the enclosing `navigation-list-item` is `active`, so it needs to be generated only when `page.url == node.url or page.parent == node.title or page.grand_parent == node.title`.

(cherry picked from commit db50f282bab1e98397cc7434a811b8b7da2fe6dc)

(cherry picked from commit 6684f7c7faa15d6d59df35fbff9ea6666634d754)

(cherry picked from commit eeb3f342b17a744d0c2b2f0360359fa3276f8abd)

(cherry picked from commit 7fb79c2018b979fdf917f427ca5d3f2451f3265d)

(cherry picked from commit 8aa0899facd01f689692fccdb338673f5e9a9fbd)

(cherry picked from commit bab3437a1feefc49213e1e787db0451491aca9b9)

(cherry picked from commit 52b0bced5d235d7557413e064f3841ea774d9063)

(cherry picked from commit ac42a41ae3e36b002df52882be296c01873c0e5b)

(cherry picked from commit dffb2706a158784e2f3091f895a868e373683bc8)