SOLIDPOD: Option for LOGIN button to always login

[gjwgit]

Description

The LOGIN button should have an option to tryCachedLogin: true to allow the app developer to force the LOGIN button to always log in and ignore cached login. Using the cache is pretty handy if I am always using the same WebID but gets tricky if not.

This might be an issue only when we have multiple WebIDs but in general it seems there is no way for an app to logout of the Pod so I can log into another WebID, except by the use of the logout button in the app itself.

I propose that LOGIN will not use any cached login information and always prompt to login to a pod if tryCachedLogin is false. A CONTINUE will use the cached login if already logged in (as it does now) or will prompt to login when required (which it does now).

Might need some visual clue as to which scenario we are in. If LOGIN text is bold font then we know there is a cached login and it will be used.

[cdawei]

Might need some visual clue as to which scenario we are in. If LOGIN text is bold font then we know there is a cached login and it will be used.

Perhaps a more explicit visual clue (e.g. a switch widget that a user can interact with) might be easier for a user to figure out this intention.

[gjwgit]

See discussion in #217