v1.6 - Draw me a genome, using P(y)rodigal

This is the sixth minor release (v1.6) introducing the creation of circular genome/plasmid plots and fixing false de novo gene predictions by Prodigal.

Compatible database scheme version: 4

New features:

• Creation of circular genome/plasmid plots using Circos: #163 #166

Improvements:

• Replace Prodigal by pyrodigal fixing false gene prediction scores on reverse strands: #149 #165 (Thanks @jhahnfeld, @althonos)
• Improve tRNA product descriptions including anticodons: #170 #173 (Thanks @acvill)

Fixes:

• Fix issues with IUPAC ambiguity codes on tRNA prediction using tRNAscan-SE: #150