Allow to override configuration from cmd line.

Add `-o` option to allow options overriding from the command line. For
example, one can specify

	pkg -o DEBUG_LEVEL=10 update

to enable extended debug for this specific pkg invocation.

Requested by:	az
Issue number:	#731
Update libucl to latest version
Fix issues with upgrading.
Fix some more issues with the solver.
Start SAT optimization.
Use proper Sx for referencing another section
pkg-add: Fix -A to properly mark package as automatic

Issue #732
Reported by:	mat
Fix pkg2ng on NFS

Submitted by:	Jilles
Issue ##734
pkg2ng: Update FORCE_POST patterns from ports r344469
pkg2ng: Show a message when running pkg check -Ba
pkg2ng: Fix stray %s(), pkg_emit_errno() does not accept format/va_args
Warn about conflicting options in env and cmd line
Add helper script for aspcud external solver.
Rework the internal solver.

1) Now all clauses are linked to the variables
2) Fix upgrade job processing
3) Fix the internal solver algorithms
4) Print total jobs in the universe
5) Add extensive debuggig
Fix CUDF integration.
Use trendy criteria by default.
Use only one SAT model.
Fix CUDF solvers integration.
Fix jobs iterators.
Command line options redefines env options.