added sunniness field to plantings
generalised sunniness into a variable for later reuse
allow blank sunniness value as well as nil
added sunniness to the planting form
display sunniness on planting page
Merge pull request #159 from Skud/sunshade

Sun or shade?
sort plantings
Merge pull request #162 from phazel/sorted_plantings

sort plantings
Broke recent plantings/posts out into partial

... which is now displayed on both the signed in and signed out
homepages.
improved date/time formatting

we set defaults for date and time formatting (and override them in a few
places)
delegate crop system name and url
Added a display of interesting members to the homepage.

Also merged in the latest dev (hence some minor changes to non-homepage,
non-member stuff).  I think I messed up the merge a bit :-/