(Bug 4504) : Removed JSON module version 1.0 from dw-free.

This branch can't be merged into production until we've completed the
JSON upgrade - Net::Twitter requires 2.x.
(Bug 4504) : Removed the test error now that fu has fixed the form
defaults problem
(Bug 4504) : updated _to_co_urllength and config-local documentation

The urllength will now be aquired automatically from twitter and stored
in memcache unless overridden from config-local.
(Bug 4504) : Use LJ::Trim on new prefix text
(Bug 4504) : Cleared FIXMEs & made tweettext_from_entry (hopefully) unicode-safe

Also changed from using ... to using unicode epsilis when truncating.
(Bug 4504) : Tidied up comments, removed some FIXMEs.
(Bug 4504) : Added check on twitter settings page for length of prefix text.
(Bug 4504) : Removed allowance for communities crossposting, since
communities can't crosspost.
(Bug 4504) : tweettext_from_entry can now handle ludicrously long prefixes
(Bug 4504) : Clarified text.
(Bug 4504) : Moved checking of twitter errors to new function

Created _check_twitter_error.
(Bug 4504) : Tidied up temporary files & capitalisation of file & module names
(Bug 4504) : Set the username at the end of the oauth sequence.