Report majority rule assembly as single contig

[Casey Dunn]

At present, each edge in the majority rule consensus is reported as its own config, along with an associated posterior probability. This obfuscates the linkages between the contigs that are supported by the data. It also leads to several distinct applications of the term 'contig' (which is a path in the assembly graph, but an edge in the report).

The report should include one sequence string per contiguous path in the assembly graph. Posteriors should be encoded separately as annotations of these sequences.

[Mark Howison]

Fixes #1: majority rule consensus FASTA output

→ <<cset 3e9e218a68d8>>