[SUI] Merge 2.4.1

[ColinFrick]

Feature Request

Description

Merge Semantic UI 2.4.1 release

I propose only to merge following changes:

• Embed - Embed will now correctly remove DOM metadata on destroy Semantic-Org/Semantic-UI@620cb3f
• Grid - Fix issue with very relaxed vertically divided grid having wrong margins on dividers https://github.com/Semantic-Org/Semantic-UI/blob/1724b3eff4d33ac90592ec85685ea6ef97022371/src/definitions/collections/grid.less#L1118-L1119

Will be fixed with #172:
Dropdown - clearable dropdown now works with dropdown that arent on:click, like hover or manual triggers.

Already fixed with #135:
Modal - Fixed fullscreen modal having incorrect left offset with flex modals

Build system update to gulp 4 is almost finished. Additionally we have less 3.5.0 support since #97

[lubber-de]

Your fixes for modal and clearable are a bit different to Jack's ones from sui. Have you found out his fixes are still not working?

[ColinFrick]

@lubber-de We have a different implementation for clearable dropdowns.
Additionally as our code base diverges more and more, we can't merge just anything from SUI anymore, even if Jack's fix works in SUI.

[y0hami]

Merged.