in all remaining examples, replace bp.parse_args by bp.parse_commandline + direct overwriting of plotargs (#1071, #1065)

This reverts merge request !2766

Adapted also 'publicmode.erb' and 'testmode.erb' files.

* variable:
'sm' -> 'test_mode'

* files:
longmode.rb -> publicmode.rb
shortmode.rb -> testmode.rb