Added downloadable materials report

[TestaDiRapa]

New Features

• Added a button to download an Excel report of all the material. Closes Add downloadable material report #58

Bug Fixes

• Fixed a bug that didn't allow to select more than one box at a time when adding/removing materials in a box. Closes Cannot remove multiple boxes even when it should be possible  #59

UI Improvements

• Now it is possible to manually insert a number when adding or removing materials in a box. Closes Allow to insert the number when selecting the number of boxes to remove  #60
• Added an indicator for when there are no more units available for a material