Revert a hack that blocks scope flexibility

Hardcoding the scope disables the settings that are defined in the application itself, and blocks per-implementation scope configuration.
The scope can be defined when creating/updating a LinkedIn app, so it's useless to hack it.
The scope should be hardcoded only if it can be set elsewhere, out of the library, so that implementation can define their own scope directly, so not as a constant.
Application scope setting seems the most flexible solution for the moment.
Enable extra parameters from config to be passed into OAuth1 authorizeUrl.

It is often necessary to request the permissions of a given service during authorization, and the OAuth1Client allows for an "extras" parameter, so I am passing the provider's config["extras"] array to the api's authorizeUrl method. This may also benefit the OAuth2 provider, but I haven't gone there yet.
Removed duplicate empty displayName logic block

The code was checking for an emptyDisplay name before trying to set the displayName based on the friendly name. It was also swapping the firstName and lastName.
    
This changes removes that code block and fixes the logic in the code.
two paypal providers, oauth 2 and openid
Fixes #155 Ability to trust forwarded sessions
Check if primary url exists

Some profiles might not have set a primary url (mine doesn't), so better check for it first.
Removed MySpace
Merge pull request #161 from discant/master

Removed MySpace from installation instructions
Merge pull request #156 from jhubert/patch-1

Removed duplicate empty displayName logic block
Removed redundant check.
Merge pull request #160 from mattsches/patch-1

Check if primary url exists - Google provider
Merge pull request #158 from nineinchnick/paypal

paypal, two providers, oauth 2 and openid
Merge pull request #146 from Facyla/patch-1

Revert a hack that blocks scope flexibility - LinkedIn provider
Updated the Facebook Provider to support the auth_type parameter in the login dialogue.
Adding default value for trustForwarded config
Merge pull request #86 from F21/master

Updated Facebook provider to support "auth_type" in the login dialog.
Merge pull request #150 from stephenr85/patch-1

Enable extra parameters from config to be passed into OAuth1 authorizeUr...
Merge pull request #159 from jeffery/fix-trust-forwarded-sessions

Fix #155 trust forwarded sessions for Facebook auth