[doc] Fix building the doc due to previous patch using webp instead o…

…f png (#177)

[version] Update version to 1.6.0 (#163)

[release] Version 1.5.0

[version] Update file headers and version to 1.5.0-beta

[version] Update version to 1.4.1

[changelog] Update date in changelog

[dev] Fix archive generator

[changelog] Update changelog

[changelog] fix date

[doc] Update readme and manpages