Fix issues caused when a traveler is deleted

All legs, lodgings, and events are updated.
Dialog buttons reformatted with smaller padding on left & right.
Method verifyTravelers() added to TravelerGroup
Method removeTraveler() added to TravelerDialogFragment
Method fetchTraveler() added to TravelerDbAdapter
Refactor use of generic colors

Changed "red" to "data_entry_error".
Changed "black" to "data_display_only".
Remove dummy Dev.log entries
Merge pull request #24 from nerychapeton/(V6)-Fix-issues-when-deleting-traveler

(v6) fix issues when deleting traveler