Trac #15505: Add missing relations to braid group
Trac #15488: Fix misplaced sig_on() statements inside try
Trac #15422: Fix p-adic factorizations for non-squarefree polynomials
Trac #15433: OS X's accelerate framework no longer pretends to be atlas
Trac #15301: fix a link to the PDF version of PREP tutorials
Trac #15007: Alias .diff() and .differentiate() to .derivative() in
polynomial rings
Trac #11934: Add a doctest to confirm that full_simplify() doesn't affect the imaginary part of an expression.
Trac #15392: support for minimal models of projective maps
Trac #13352: Use mpn_popcount() for bitset_len(), clean up bitset interface
Trac #10093: Clean up documentation of sage/misc/bitset.pyx
Store actual tarball name in package metadata.
Use stored tarball name for downloading.
Merge branch 'master' into ticket/14968

Conflicts:
	build/pkgs/sagenb/checksums.ini
Trac #10093: Raise ValueError when trying to init a Bitset with capacity 0
Trac #15150: Implemented NCSym.
switched the large Cremona ellcurve database to the new git directory layout
adding first files database_symbolic_data to build/pkgs
updated libogg and libtheora, fixed sage-git layout
add fixed openssl
added more requisites for git layout