Improvements to the UI when updating or deleting a lot of elements at once

[mikesnoeren]

Some small changes that would make the UI more polished:

• Allow the user to choose how many elements are displayed.
  How: Add options 50, 100, 200, all. When option all is chosen this could bring up some performance issues, which the user should be prompted about when selecting this option once every session.
  Why: When you have ~500 products, and you are testing an import for example, it's very annoying to have to delete all those products.
• Add checkbox select all when selecting the 100 displayed elements
  This is an alternative for the above.
• Loading indicator when deleting or updating statusses of multiple elements
  Why: It would be nice to get an indication of the process, especially if one of the above points gets implemented. Simply showing "Updating (49/500).." would be enough.