extract collection date without time

[Ha-nn-ah]

Modified 'collection_date' handling to accommodate (two) time formats; otherwise, there occurs an error in step 4. This update ensures panX processes 'collection_date' correctly by ignoring time and proceeds solely with the date.

[fbaumdicker]

@Ha-nn-ah recently did a panX analysis of all reference strains from NCBI. For some reference strains, the collection date format includes not only a day, but also a time. Day and time are split by the letter "T" which confused panX as it assumed that any character string in the collection date corresponds to a month. This should fix this.