Fixed disabled dark theme icon not being included in manifest file.
Changelogs are not required anymore to create an update.xml file. If no
valid changelogs are found, the generated update.xml file will simply
have an empty description.
Ranamed 'changelogs' to 'changelog_folder' and added
'changelog_extension' property to configuration and updated readme
accordingly.
Updated NPM version to 0.1.2.