PROTON-324: Refactor Perl support for working with arrays and Data objects

Renamed the TypeHelper class to Mapping to be more like the Ruby
language. Deleted the previous qpid::proton::Array class since it
tightly coupled the developer's code to Proton where it should not do
so.

Provides three new methods:

  qpid::proton::put_array_into - put an array into a Data object

  qpid::proton::get_array_from - gets an array out of a Data object

  qpid::proton::get_list_from  - gets a list out of a Data object