Changelog entry for 1.20

Merge branch 'lintian-fixes' into 'master'

Fix some issues reported by lintian

See merge request wouter/fdpowermon!1

Tagging fdpowermon 1.18

Tagging fdpowermon 1.17

Tagging version 1.16

Tagging 1.15

Release

Release 1.13

Release 1.12

Tag the 1.11 release