Resolve "extend token validity to 30 minutes"

Reason: the server is running two separate timeouts:

• one for the token, renewed automatically from the interface;
• one for the cached database changes; it does not depend on the read/write mode and never handled externally. The second timeout is affecting the operations: the timeout can happen while the key is still in creation

Solutions:

• on the server side, the renewal of the jwt renews also the timeout for the subsystem cache if in write mode (otherwise it reset the cache)
• on the client side, the renewal function keeps track of the begin of the write session; it still performs automatic token renewals but, after 30 minutes of write mode, it prompts a choice for the user: the dialog has a timer (visible as a countdown), at the end of which, the session is reset anyway, if no option is provided.

Features:

• handling of the subsystem cache timer
• dialog for renewal of long write session
• enabling timeout for l1ce-toast dialog
• adding l1ce-countdown element

Extra:

• disentangled database configuration parameters from database class; also timeout is configurable now

Closes #128 (closed)