Merge branch 'release/2.0.5' into develop
Set the scope parameter to not be required by default. Fixes #43
If scope parameter is required and there are not requested scopes AND there is no default scope set then fail

Should have been included in with previous commit
Allow for multiple default scopes. Fixes #42
Renamed scopes.key to scopes.scope. Updated ScopeInterface and PDO/Scope. Fixes #45
Don't delete old sessions when issuing new access tokens using the Password or Client Credential grants. Fixes #32
Added removeRefreshToken method to SessionInterface
Update associated scopes if requested in refresh access token. Fixes #47
Merge branch 'feature/refresh-token-rewrite' into develop
Accidentally used PHP 5.4 style bracket
Move zetacomponents/database to "suggest" in composer.json. Fixes #51
Fixed two probems in access token check 

1) The method returned the wrong result in case when the access token itself contained the string "Bearer".

2) When using cURL, the request is sometimes send twice (in my case when the first request returned a 404 error), and the Authorization header of the second request is doubled, so that you get a "Authorization: Bearer XXX, Bearer XXX". This case is checked now. (BTW: Tested with the current PHP version 5.4.15 on Windows.)
Updated @ziege's patch to overcome awkward access token definition requirement (i.e. access token can have a space in it) and also optimised code. Fixes #52
Added rotateRefreshTokens() method
Added missing semicolon
If rotateRefreshTokens() is true then associate new access tokens
Updated tests
Merge branch 'feature/refresh-token-rotation' into develop
Added associateAuthCodeScope() method
Added getAuthCodeScopes() method