feature: modify metadata_enricher to only write relevant metadata found

[msramalho]

Currently all metadata is extracted from a file, the goal is to have an option in this enricher that only extracts metadata if specified from a list, example: [gps, datetimes, author]

So the gps would only find lat/lon information, example parsing logic from the direct output of exiftool:

def extract_coordinates(metadata):
	d_metadata = {l.split(":")[0].strip(): l.split(":", maxsplit=2)[1].strip() for l in metadata.split("\n") if ":" in l}
	gps_metdata = {}
	for k in d_metadata:
		kl = k.lower()
		if ("gps" in kl or "latitude" in kl or "longitude" in kl) and len(d_metadata[k]):
			gps_metdata[k] = d_metadata[k]
	if len(gps_metdata): return gps_metdata
	return False

Something similar could be designed for create_date!=modify_date or other relevant information found.