Add new amount dict format for appbase and other improvements

Account
* Remove set_next_node_on_empty_reply(True) for get_account_history calls
* Retry when native get_account_history raises ApiNotSupported with condenser_api
* Refactoring and use of addTzInfo from utils
* Improved logic and bugfixes for history()
* print_summarize_table moved from cli.py to Accounts
Amount
* New appbase amount dict format supported
cli
* Refactoring of print_account_table
Comment
* New appbase amount dict format supported
utils
* addTzInfo added to reduce code
* testing nodes added to get_node_list (disabled by default)
Vote
* votee added
* printAsTable improved and PrettyTable used
* get_list added to recieve vote properties as list
* print_stats added but not finished yet
* ActiveVotes improved with start and stop to limit stored votes
Witness
* return_str added to printAsTable
unit tests
* more unit tests for history and history_reverse
* unit test for new appbase amount format added