Version 0.5.0

Changes since 0.5.0-rc:
* locale prefix support
* download client from user page
* hotfix to make webapp work with rack again
* ensure permissions are preserved when copying customization files. (#4623)
* Return 'provider.json' via a controller, to better be able to control the response headers
* document new way we deploy couch design docs
* remove outdated views that cause errors
* only emit pgp keys if they are actually set
* ensure auto_update_design_docs is false
* switch to using dl.bitmask.net
* remove manual 'gem minitest'
* default pricing, privacy policy and tos pages
* default footer with links to privacy policy, tos, pricing, about us, contact
* upgraded bootstrap to latest in 2.x series
* move #masthead out of main templates
* customizable 'bye' page for when a user leaves
* fix js platform detection
* applied mcnair's changes to privacy policy
* untracked files in deploy are in gitignore - #4953
* gitkeep empty folders for config/provider and config/customizations
* integration test with en-EN language
* ensure record removal after tests
* log failing integration tests with screenshot and serverlog
* stop taking screenshots inside tests