Merge pull request webodf#918 from vandenoever/settings

If there is no <office:settings/> element, save an empty <office:document-settings/> element.

set version number to 0.5.9

set version number to 0.5.8

set version number to 0.5.7

set version number to 0.5.6

set version number to 0.5.5

set version number to 0.5.4

set version number to 0.5.3

set version number to 0.5.2

set version number to 0.5.1