Reorganize and refactor Navigation

[gregrickaby]

As discussed internally, we're going to break navigation components (mobile, desktop, etc...) out into separate partials.

[gregrickaby]

Just a follow up... I refactored this on a recent project and would love to demo it. Maybe bring it into wd_s!

[jomurgel]

Branch: https://github.com/WebDevStudios/wd_s/compare/theme/navigation-refactor

I've made several changes in this branch.

• Removed the _mobile-navigation.scss partial which appeared to be a carry-over from the older mobile-navigataion setup.
• Created a navigation folder inside modules and moved navigation partials in there.
• Consolodated navigation into global (contains .menu), main, mobile (contains off-canvas) and post-navigation.
• Moved the post-navigation styles out of _navigation.scss into its own partial in modules > navigation.
• Moved the global link styles into it's own _links.scss partial because it's independent from any navigation (presumably) and added a transition helper.
• Removed the hamburger menu styles from _icons.scss both because it doesn't really belong in there and to consolidate all navigation styles into the new menus folder.
• Added support for multiple nested levels in the mobile-menu.js
• Added styles to rotate dropdown arrow at each level.
• Adds script to prevent body from scrolling when off-canvas navigation is open.
• Moved some of the basic container styles for the main navigation into the _header.scss partial to consolidate all of the structural elements.
• Fixed some positioning problems with the mobile hamburger on mobile if the admin bar was present.
• Reworked the transitions on the hamburger button to make them a little less choppy using transforms rather than absolute positioning. Tested working still in IE11, Edge, Safari, Chrome, Firefox and Opera 😁

Before

After

• Decreased the max transition duration from 0.8s to 0.5s in the transitions helper partial. Adds transition for hamburger specifically.
• Reworked the header/nav area on desktop to fix some basic render issues.

Before

After

• Removed as much fat, or consolidated as much as I could to clean things up a bit.
• Added table of contents to _mobile-navigation.scss partial for ease of use.

Opened issue #334 to potentially discuss moving related styles together as I did here. Keeping nav-only buttons in with navigation vs with buttons.

Opened issue #333 to potentially discuss reworking navigation to target and add classes to each submenu level individually rather than adding a global is-visible class.

[gregrickaby]

@jomurgel This looks fantastic and is exactly what I had in mind. 🥇

Go ahead and open a PR!