fixes for expenses additioanl expenses

there was an error when no expenses were provided
added some help annotations
added button for removing custom expense

fixed float numbers alignment on print
added meals summary in print view

added english subtitles
minor improvements for print view
other fixes
improved expenses list
fixing tooltips
fixing tests for Travis
added caching exchange dir table

as it changes only once per day
trying to integrate mongodb to store rates

experimenting... it needs a lot of refactoring