Fix equality test on showSyncButton return value

For correct detection of error message being returned.
Improve F1 authentication error messages
v0.3: Correct authenticate redirect and session start issue

being called too late in the WP process
Improve error messages for retrieving access tokens
Improve error messages for credentials based auth
Improve js error messages to handle no message field
Add methods to session object for handling f1 access tokens
Add all server settings to session upon authentication

so that settings used to authenticate are persisted throughout the session, even if they are changed in WP admin after authenticating.
Fix logic of setting Fellowship One options on init
Add no direct access check to all class files
Delete original oauthclient file, not being used
Update version to 0.4
Update manual tests file