improve filter ui

[rodolakis]

• replace spin box with QDateTimeEdit for dates
• replace drop down menus with input boxes
• explore tooltips to display hints for input boxes

[rodolakis]

Maybe look at this: https://forum.qt.io/topic/41123/solved-search-filter-inside-combobox-qcombobox

[prjemian]

@olliviergassant Perhaps this issue can be closed now?

[olliviergassant]

Issues have been resolved