Photon: Tweak data-recalc-dims regex.

The regex adding the data-recalc-dims should not care how many whitespace characers there are between the closing tag and the possible following link tag.
Tiled Gallery: Split data-original-size getter.

Split the function that produces the string into data-orig-size (for carousel) into two. When meta width and height are separated, we avoid having presentation logic pieces in the model object.
Tiled Gallery: Pass context to partials as param.

Avoid having to litter the object instance (by putting stuff into `$this`) for partials, and allow the `template` and `partial` functions take a context array whose values will be extracted to the symbol table. Context required by partials is now passed via the context param.