Added basic CSV import/export.

Also simplified and fixed bugs regarding data/gui updating on the moneynode list
and details activity.
Simplified data/gui updates on category list.

TODO: Maybe abstract these updateGui/updateData functions?
Fixed row bg color on user list and keyboard appearance on user select.
Graphical enhancements to money node details activity.

Namely, make percentages on the stats list view have all the same width, show
title of activity, increase label font size on the pie chart.
Fix date selection on month wraparound and remove trans no longer on period.

That's what you get for not reading the documentation carefully. roll() doesn't
change higher fields so when subtracting a day to the 1st of March, one'd get
31th March. Replaced roll() with add() for correct behaviour.
Fix validation on edit and cascading of deletes after edits.

Turns out that SQLite applies the CASCADE DELETE clauses on INSERT OR REPLACE
queries. Removed the insertWithOnConflict with pre-check of existence in the
database or not (by checking if there's a known id).
Fix appearance of DrawablePicker on high dpi devices

Also corrected overflow of total balance on MoneyNodeDetails with high balances.