* reading caption and title from several tags with several tests added
minor bugfix for date conversion to MS
optimization: break sidecar loop, when first sidecar is found
* Removed the SideCar Type to make reading sidecar data just as generic as reading the embedded exif data
* Moved metadata-mapping into separate function to prepare for reuse
* Most sidecar metadata is now read with the same function as embedded metadata (for photos). Fixed a bug with rating: 0 being ignored
* added new test for special chars and timezone
* merge incoming changes
* xmp rating fix - 0 is a value. prep for xmp timestamp handling
* refactored mapping of metadata into smaller functions
* consolidated GPS coordinate mapping
* simplification of sidecar date reading logic
* Moved date mapping code into one function - fixed testdata - did not yet resolve offset bug
* CreationDateOffset is now mapped from Sidecar timestamps. Tests updated accordingly.
Total: changed sidecar reading for video to shared reader and fixed tests accordingly (more data is read now)
