expenses list: group expenses on days
expenses list: refactoring. Options menu disabled
ExpandableListFragment added (https://gist.github.com/mosabua/1316903)
expenses list: expand/collapse on day items
expenses list: setRetainInstance(true) to save expanded state
expenses list: styling, group icons added
ExpandableListFragment: deprecated FILL_PARENT changed to MATCH_PARENT
expenses list: styling