Support sticky fields

I'm adding more cards on my phone than usual these days. I noticed that sticky fields are not supported, i.e. fields get emptied out after a card was added even though the *Remember last input when adding* field option is set.

Background: I track references for almost all my cards. When I'm adding cards while reading a book the reference will stay mostly the same with exception of the page number. This feature saves a lot of typing / copy-pasting.

PS: I'm not too happy with the location of the code.