Update license file

Rename to LICENSE, as the filename COPYING usually suggests GPL.
(Use git diff -M40% to see this commit as a rename.)

Use the less ambiguous term "MIT/Expat" license, as there are several
different licenses sometimes called the "MIT license".

Update years in the copyright notice, and add note about year ranges.

Reformat the last paragraph -- there are no text changes.
Omit control files and README.md from release tarballs
Add licensing boilerplate

(The makefile also has small contributions from Bob Handsaker
and Pierre Lindenbaum that are not legally significant for
copyright purposes.)
Update copyright years to reflect historic changes

(kprobaln.c also has small contributions from Lee Baker and Petr Danecek
that are not legally significant for copyright purposes.)
Add copyright notices and licensing boilerplate

Some files include copyrightable portions copied from other source files,
leading to copyright years apparently prior to their creation:

bam.c contains bam_fetch() from bam_index.c; bam_lpileup.h and bam_plbuf.h
are copied from bam.h (so that htslib-based code can use these functions
without #including the legacy bam.h); bam_plbuf.c is copied from the
former bam_pileup.c; bam_split.c contains some code based on similar
code in stats.c.

For changes by Heng Li, the applicable copyright notices reflect
that he was at Sanger until October 2009 and at Broad thereafter.
Add copyright notices and licensing boilerplate

(There are also small contributions from Lee Baker (all files) and
Peter Cock (bedcov.c and faidx.c) that are not legally significant
for copyright purposes.)
Add copyright notices and licensing boilerplate

(There are also small contributions from others that are not legally
significant for copyright purposes: Erik Aronesty (sam_view.c),
Lee Baker (bam_sort.c), Christian Brueffer (samtools.1), Vince Buffalo
(bam_aux.c), Peter Chines (bam_sort.c), Bob Handsaker (bamtk.c),
Manuel Holtgrewe (bam_sort.c and samtools.1), Nils Homer (sam_header.c
and bam_sort.c), Mike Lin (bam_sort.c), Sam Nicholls (bam_sort.c and
samtools.1), and Brent Pedersen (sam_view.c).)
Update copyright years and reformat licensing boilerplate

(There are also small contributions to bam.h from Nils Homer (whose
contribution has since been moved to bam_tview.h) and Dan Kortschak
that are not legally significant for copyright purposes.)
Update copyright years and reformat licensing boilerplate
Fix copyright notices and reformat licensing boilerplate

Copyright and licensing boilerplate was somewhat naively added to these
files in June and October 2013.  Significant contributions have been made
by Peter Cock (bam_mate.c) and Pierre Lindenbaum (bam_tview.c), and this
commit restores the notices acknowledging these contributions that were
previously omitted.

(bam_tview.c also has small contributions from Peter Cock, Bob Handsaker,
and Nils Homer that are not legally significant for copyright purposes.)
Add copyright notices and licensing boilerplate

(bam_index.c also contains small contributions from Nils Homer,
Lee Baker, and Nicole Washington that are not legally significant
for copyright purposes.)
Add copyright notices and licensing boilerplate
Reformat copyright notices and licensing boilerplate
Add copyright notices and licensing boilerplate
Merge copyright notice and licensing boilerplate additions

For changes by Heng Li, the applicable copyright notices reflect
that he was at Sanger until October 2009 and at Broad thereafter.