Add photo album support

[jonbullock]

Add photo album support so I can eventually replace the need to run Gallery.

[Riduidel]

I had a proposal, but I think it requires a few preliminary works. Namely #115 (to avoid crazy big index pages) #9 and/or #18

[jonbullock]

I haven't thought much more about this. My initial thought was to group photos into album folders and render a page (of paginated pages) per album with auto generated thumbnails on. I had thought to keep the photos separate from the text based content but it doesn't have to be this way.

I was also thinking about having a special file in each album folder that defines metadata for the album, say for rendering but parsing this data from the photos themselves is another option.

[jonbullock]

Linking #101 and #115