refactor line_extension DAO tests

all_of assertions aren't as clear as equal_to when a test fails
split tests into smaller units
implement find_all_by_line_id in line_extension service
implement find_all_by_line_in in line_extension DAO
implement find_all_line_extensions_by_line_id in incall DAO
Merge branch '5003_restapi_incall_list'