Feature/4101 update ck editor version

[skamphuis]

Closes #4101

Summary

I updated CKEditor to version 4.15.1 and made the required/appropriate changes for that:

• moved DNN icons and images out of CKEditor folder
• changed "broken" javascript in EditHTML.ascx for resizing the editor after window.resize
• updated version numbers for CKEditor in code (mainly for file paths)

[bdukes]

Thanks!

This will certainly need some real world testing, but all of the changes look good.

Once #4374 is merged, I have a branch where I've rebased this PR on those changes. Thanks for the very clean commits, it made the rebase very straightforward :-)

[donker]

Thanks for working on this editor provider!

[bdukes]

FYI, I've pushed the rebased commits to your branch since #4374 was merged.

[skamphuis]

While testing some more today, I noticed 2 plugins and a skin where missing from the updated CKE:

• plugin dnnpages
• plugin wordcount
• skin moono (used for the popups)

the 3 commits (just now) add these to the CKE folder.

[skamphuis]

Another two commits needed after testing. Link popup didn't seem to work.

• Had to remove the easyimage and cloudservice plugins, to prevent console warnings (those plugins are not included, but seem to be known in CKE anyway)
• DefaultLinkProtocol property (new in CKE 4.11) is needed for the link popup to work.

[bdukes]

(nit) Can this get moved inside the namespace declaration, please?

[skamphuis]

Sure, I'll fix that.

I noticed changes like this recently. Do you know the benefits of that?

[bdukes]

It's primarily a style rule, but it does have some minor benefits (described in the StyleCop rule docs)

[skamphuis]

That makes sense, thanks.

[bdukes]

Thanks!