Refactor out use of anyhow

[algesten]

This relates to #106

Worth noting:

• I decided to keep anyhow for the examples (making it a dev-dependency).
• Non of the subcrates git versions are checked in. I'm waiting for @rainliu to release them.
• There are tests failing on macOS on the master branch. This is the same in the PR.

test data::data_channel::data_channel_test::test_eof_detach has been running for over 60 seconds
test data::data_channel::data_channel_test::test_eof_no_detach has been running for over 60 seconds
test media::dtls_transport::dtls_transport_test::test_peer_connection_dtls_role_setting_engine_client has been running for over 60 seconds
test media::dtls_transport::dtls_transport_test::test_peer_connection_dtls_role_setting_engine_server has been running for over 60 seconds
test media::ice_transport::ice_transport_test::test_ice_transport_get_selected_candidate_pair has been running for over 60 seconds
test media::ice_transport::ice_transport_test::test_ice_transport_on_selected_candidate_pair_change has been running for over 60 seconds
test media::track::track_local::track_local_static_test::test_track_local_static_payload_type has been running for over 60 seconds

Close #106

[rainliu]

@algesten, thank you for the efforts refactoring all crates' error handling. Last crate to be done. :)

[algesten]

@rainliu so close to the finishing line :)

hopefully this passes cleanly now.