Task 40692
Various changes to import/export (mainly) UIs:
* default to excel & "full" (non-import-compatible) export
* auto-detect encoding of CSV using chardet
* remember column -> field mapping after having imported a file (useful
for repeated imports where auto-matching failed)
* better handle localised booleans & column names
* automatically select source list view's fields when exporting
* better integrate import templates feature and add a number of templates