Clarify "Translations" feature in Admin Panel

[cbunicef]

Since we have multiple translation features, it would be useful to clarify which are used for which purposes, especially the "Translations" item in the Admin Panel menu which is prominent.

Please add this text in the "Translations" Admin Panel section, underneath the page title:

Make customizations to the website interface text elements that are not content-based - for example the text of the "Login" button. Customizations are made by language, and override the default translations for each language.