Closes#603.
Other changes:
- Move the "Removing services" section to earlier in the doc - it is important!
- Consistently use 'strings' instead of "strings" in example code
- Mention briefly how "spawn_service:" false affects plugins
- Mention the "dynamic" channel handling added in 2.0-alpha3
- Move nick/ident/host/gecos fetching from services_support into functions
- Remove the unused 'ident' argument from ServiceBot
- Rename the 'nick' argument in ServiceBot to 'default_nick'
- Define default nicks for the PyLink, Automode, and Games services