Seq-qc

- Fixed bug in which demultiplex_by_header mean, median, and sd output statistics were not correctly formatted as floating point numbers

- Changed the way that input compression is detected to match that of output compression.
- Fixed bug in qtrim where an error would be thrown if a singles file is not specified with paired reads.

- Fixed cropping in qtrim, which broke when cropping definition was reverted back to that of earlier releases.

- Removed tool for performing filtering based on maximum-error thresholds.
- Changed name of demultiplex_headers to demultiplex_by_header and massively re-worked the program to be more flexible and useful.
- Added the ability to use multiple CPUs to speed up trimming with qtrim.
- Improved readability of code by adding comments and grouping related statements together, when possible.