Add config options to limit number of stored events and actions

[bw-hro]

At the moment all emitted events as well as requested actions will be saved in memory. For long running applications with limited resources this could become a problem.

Possible attempts:

• limit number of actions/events that will be stored.
• limit duration how long to keep objects in memory (e.g. 1hour, 1day, 1week, ...)
• limit memory used e.g. 256MB

when limit is reached

• Oldest element will be removed to store new one. (like rolling appenders known from logging)
• removed objects could be persisted as backup. e.g. in a text file, sqlite db, ...