Add source: and sourceurl: items to image headers for nicer layou
text cleanups
Image source line improvements: can take one source, or an array:

usage:

  source:  "[My link](http://biglink.net)"

-or-

  source:
    - "[My 1st link](http://biglink.net)"
    - "[My 2nd link](http://biggerlink.net)"
    ...