Allow session reusing to reduce login flood

[ttycelery]

One of the downsides of not storing password/session is the need to log in every time a request to the API is made. This also don't look good in the logged in devices page on SIMASTER.

Caching the logged session is not secure, but having it as an option will be nice (should not be a default setting). This way, some users can let their session token cached and have a more efficient and less floody login history.