v.0.7.0

• Refactoring/image handling (#46)
• Adds support for three missing diagram types (#43)
• Fix retrieve typo (#47)

IMPORTANT CHANGE:
Plugin-Option "DownloadDir" is not supported any more and will throw an error.

Very special thanks to @oniboni for the refactoring
Also thank you @Epithumia and @al-cheb for their contributions