Assisted digital content changes

- 2 existing guides updated
- 1 new created
Prevent stumble when reading

Unco-ordinated -> uncoordinated
Fix typos
Simpler, less awkward title
Fix organisation name
Merge pull request #338 from alphagov/assisted-digital-

Assisted digital content changes
Fix markdown
Fix markdown
Remove unnecessary heading from 'Helpdesk' page
Update subtitle of 'Hosting' page
Rewrite of 'Accessibility testing' for style

bullet lists, removal of banned words, plain English etc.
Rewrite of 'Analytics tools' for style

bullet lists, plain E, removal of banned words...
Rewrite of 'Configuration management' for style

bullet lists, removal of banned words, plain E, voice...
Rewrite of 'Cookies' for style

bullet lists, voice, removing banned words etc
Rewrite of 'Information security' for style

bullet lists, removing banned words, plain E, layout etc
Rewrite of 'Progressive enhancement' for style

bullet lists, removing banned words, etc
Rewrite of 'Release strategies' for style

bullet lists, plain E, removing banned words, voice etc
Rewrite of 'Sandbox and staging servers' for style

bullet lists, plain E, removing banned words etc
rewrite of 'Version control' for style

change link, use bullet lists etc
rewrite of 'Choosing technology' for style