Swarm 2.2.0

Version 2.2.0 fixes several problems and improves usability. Corrected output to structure and uclust files when using fastidious mode. Corrected abundance output in some cases. Added check for duplicated sequences and fixed check for duplicated sequence IDs. Checks for empty sequences. Sorts sequences by additional fields to improve stability. Improves compatibility with compilers and operating systems. Outputs sequences in upper case. Allows 64-bit abundances. Shows message when waiting for input from stdin. Improves error messages and warnings. Improves checking of command line options. Fixes remaining errors reported by test suite. Updates documentation.