Transactions/Staking rewards CSV Export

[ptrus]

There should be a way to export relevant data for an account:

• list of transactions sent/received by the account for a specific time period
• history of staking rewards (also for paratimes?) for a specific time period

Something similar to what was provided by the Oasis-monitor in the past.

The initial version can be minimal and could even start by providing the needed API endpoints (if any are missing), without preparing the actually CSV.

This task can be should be split into multiple issues/PRs.