Prepare next version wth several improvemetns

Account
* Parameter accuracy renamed to stop_diff
* Doku for estimate_virtual_op_num improved
* Several improvements and fixes for estimate_virtual_op_num
CLI
* rewards command improved and more paramter added
Comments
* Assure Amount class for all amounts
* is_pending improved
Doku
* tutorial about showing all posts of an account added
Unit tests
* test_account, test_cli and test_comment improved