Release v0.8.0

• add: matrixToDataFrame()
• add (private): get_cache_dir(), set_cache_dir()
• add: readLinesWithEncoding(), moved from fakin.path.app::read_lines()
• get_cached(): add argument "dbg"; return NULL if file does not exist
• lastElement(): do not use tail() for lists, use x[[length(x)]] instead
• orderBy(): allow to order by multiple columns
• preparePdf(): set paper to "special" if width or height are set
• readDictionary(): add arguments "fileEncoding", "...", pass on to
  readLinesWithEncoding()
• writeDictionary(): check "file" argument. Do not check the file path unless
  "file" is of class character (and not a connection)