Allow dir-style arguments for virtualenv package type

[me21]

Dir source type allows to specify destinations for specific files/directories as e.g.: modbuspp.list=/etc/apt/sources.list.d/modbuspp.list.
In virtualenv source type, we have to specify --virtualenv-other-files-dir other_files and to create other_files subdirectory with exact files layout as they should be in the target package. Would it be possible to support dir style arguments for specifying destination locations?