[Staggered orders] improvements

[Guillaume De Saint Martin]

Add options to:

1. Use existing orders as initial orders (do not create new orders during initialization)
2. Use trade history and spread to identify mirror order prices (mirror volume being computed based on the to me mirrored filled order details) => add a parameter to specify starting from when to use trade history (relatively to the bot's start time)
3. Add a delay between order fill and mirror order placement to profit from fast bump/dump increased spread