v0.5.0

Changes:

• Add --omit-types parameter to state types that should not be backed up.
• Fix problem with assets of type json throwing a file already exists error when using the --with-asset-files option, since the asset-metadata-file would be named the same as the file itself. Now asset-files will be saved in a separate asset-files folder instead of the assets folder. (Fixes #8)
• Output some more general info on start of scripts.