* check_prerequisites(): test for needed helper programs
* get_mediapool_names(): introduce new function
* get-lastwrite(): introduce new function
* get_poolmember_next(): handle selection of next tape
* mount(): handle ltfs and mtx calls in a correct order
* mount_tape(): check that mounted tape is member of selected mediapool
* ltfs_label(): use mkltfs to format and partitionin a given tape
* update_lastwrite()
* update_retensiondate()
* date_iso_to_seconds(): parse and format date-string
* date_seconds_to_iso(): parse and format date-string
* date_string_to_iso(): parse and format date-string
* typo cleanups
* update sample MediaPools.json file
Signed-off-by: Ralf Zerres <ralf.zerres@networkx.de>
