First pass at clarifying custom/standard patterns
First pass at clarifying custom/standard patterns

Once this has been reviewed, I'll copy/paste the text into 2.0, 2.1
and 2.2. (Side-note: maybe we need a better way of keeping multiple
versions in sync where they haven't changed?)

jskeet/nodatime,jskeet/nodatime,malcolmr/nodatime,malcolmr/nodatime,malcolmr/nodatime,nodatime/nodatime,BenJenkinson/nodatime,malcolmr/nodatime,nodatime/nodatime,BenJenkinson/nodatime