Improved handling of time expressions

* Corrected handling of given 12hr departure time (always interpreted as in the next 12hrs, e. g. asking for "2 hr" at 4pm = 2am, at 10am = 2pm).
* Correct inflection of time expressions: 2:14 = "ve dvě hodiny a čtrnáct minut", 1:00 = "v jednu hodinu" etc.