do not change the order of the remotes

[Basti-D]

Changelog: (Bugfix):

Fixes #613

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Do not change the order of the remotes by using the default value from the Conan API instead of -1 in add_remotes_to_conan -> _add_remote

Probably in Remotesmanager._add_remote the default argument of insert should be changed to None instead of False. The ConanAPI uses None as a the default value.
The default value False gets treated differently then None . False gets interpreted as not None , hence we go in the insert_by_index case. index = int(False) = 0`` Hence it will put always to the beginning. The current version uses index=-1`` which does not push to the end. It pushes to end -1, i.e. 1 BEFORE the last element.
`None` has it's own handling and adds the remote to the end of the remotes OrderedDict which should be the correct behavior [see remote_registry.py : Remotes._remotes].

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