Minor fixes + support timezonefinder

[rokdd]

• Some minor fixes (global do_merge not in split function,..)
• adding support for timezonefinder to find timezone by coordinates offline. (I have a huge file to split over many years in different timezones)
• timedelta for split not at midnight but for example 4am in morning (because of this the timezone is very important)

[rokdd]

Do you like my ideas or do you would solve some stuff different? I was not sure what should be a argument or just only a constant in the code.

For your background why I changed some stuff. I have a huge file with activities of google of the last 3 years. So I wanted to split them by day but not at midnight, after 4am (because I prefer to sleep at this moment). Because of the missing timezone and splitting by time I added the timezonefinder which also calculated offline the timezone by lat/lon. And last but not least I noticed that all tracks has no names, so after removing duplicates I had only half of the way left over (thats why I introduced the constant to handle this different). And thanks for your great code which works very well and was very understandable!