Configure fields on Global Snippets/Configuration

Textareas where Snippets are available can now be easily selected on
Manage/Global Snippets/Configuration page.
Revert "Configure fields on Global Snippets/Configuration"

This reverts commit c2b8559af4835fbb5f9bf1f42179e72b3597a9f5.
Revert "Revert "Configure fields on Global Snippets/Configuration""

This reverts commit ca351f51cbc92ba951fc576caabdd9881529632e.
Information about extended confgiuration page