aggregate ts in dictionary and import ts only once (#168)
aggregate ts in dictionary and import ts only once (#168)

* aggregate ts in dictionary and import only once

* import in alphabetical order

* comply with flake8-import-order

* cleanup

* typo

ros2/rosidl,ros2/rosidl_typesupport,ros2/rosidl,esteve/rosidl_typesupport,esteve/rosidl_typesupport,esteve/rosidl,ros2/rosidl,esteve/rosidl,ros2/rosidl_typesupport,ros2/rosidl,esteve/rosidl_typesupport,esteve/rosidl,ros2/rosidl_typesupport