LPS-33808 remove the word "Article" (legacy) from Web Content Administration

Hi Jim, 

in the past, the WCM was called Journal and the Web Content pieces were called Articles.

At some point we renamed the whole thing as "Web Content", however, some keys were left. This commit tries to remove all the references to the word article, but we had some difficulties with the word Content since it is uncontable and we are not sure if the expressions we have added makes sense.

Could you please review if the language keys modified or added (please ignore the deleted ones) sound good in English?

Thank you!