Remove CSS helper classes

[drublic]

The following CSS helper classes get removed from main.css:

• Image replacement: .ir
• Hidden elements: .hidden
• Visually hidden elements: .visuallyhidden
• Visually hidden elements that are focussable via keybord:
  .visuallyhidden.focusable
• Invisible elements: .invisible
• Clearfix: .clearfix

These classes were removed because they don't provide enough use cases within
modern web development. Cases are mostly handled indiviually by developers.

All the helper code is retained in the v4 branch.

Reference #1472.

Please feel free to provide feedback and discuss this commit here.

[TheDutchCoder]

I'm curious what the lack of use-cases for 'visuallyhidden' are, because I've used it in every project so far.
Mainly for the implied sectioning elements (like aside) that need a heading, but that's not always (read: often) provided in a design.

The 'visuallyhidden' class makes sure the page keeps it semantic value and exposes these elements to screen readers.

They're small classes anyway and since HTML5 BP is "delete key friendly" is it really that much of a deal to leave them in?

[necolas]

Yeah, you're right, visuallyhidden, hidden and clearfix are all useful.

[webhat]

I use clearfix, hidden and invisible quite often and won't like to see them go.

[necolas]

This was not an issue after all - #1472

We could close this.

[alrra]

I personally use all of them except .ir. So 👍 on removing .ir and 👎 on removing the other ones.

[drublic]

Sounds like a better idea to just remove .ir, as @alrra states.

[LukeAskew]

👍 for just removing .ir. Feels dated.

[drublic]

Thanks for the valuable input everyone.

[philklc]

I still use .ir all the time. Using web fonts for text in languages with a large font size (from a few to twenty-several MBs) such as Chinese, Japanese and Korean is simply not acceptable in real-world situations, .ir is still very useful in this case to display better looking headings to users.