Make SBBreakpointLocation::GetDescription() API to be consistent with SBTarget,

i.e., with 'SBStream &description' first, followed by 'DescriptionLevel level'.

Modify lldbutil.py so that get_description() for a target or breakpoint location
can just take the lldb object itself without specifying an option to mean option
lldb.eDescriptionLevelBrief.  Modify TestTargetAPI.py to exercise this logic path.

llvm-svn: 130147