Minor tweaks to native tier and DFT

Based on the feedback from @lucamghi , amend

• K Line Density: k should be small.
• Native Tiers:
  • the code should be specified with the name, e.g., VASP - high
  • Fix capitalization APW Cutoff in the GUI
  • provide the user with a hyperlink to the resources listing all supported tiers
  • change naming from native_tiers to code_specific_tier, especially on the GUI side
  • replace the GUI list in native_tiers with a search bar
• Basis Set
  • remove from DFT in the GUI
  • change to Precision Basis Set in GW and BSE GUI