Use custom namespace for asio to prevent UE collision

[mikeseese]

This PR fixes #404 by renaming the asio namespace to asio_sockio as well as any global functions in the asio library.

This PR is dependent on these PRs:

• Use custom namespace for asio to prevent UE collision asio#1
• Use custom namespace for asio to prevent UE collision websocketpp#1

This currently PR does not update the submodules as it didn't make sense to make a PR that referenced downstream repos temporarily until the dependent PRs are merged into the upstream repos. I can update this PR to have the updated submodules once those other PRs are merged, but you can also merge beforehand and update the submodules yourself if you'd prefer.

If you want to test these changes, the easiest way is to test the forked redwood branch from https://github.com/redwoodmmo/SocketIOClient-Unreal/ which resembles the final merged state (other than a change to the plugin's engine version)

[getnamo]

Good idea for interoping with other plugins in unreal. I went ahead and merged the submodule changes. Update this PR to include the submodule ref updates and I'll merge it.

[mikeseese]

Ok @getnamo, this PR is now ready

[getnamo]

I merged this, go ahead and check the master branch didn't have any regressions. Will do sanity checks on this merge later when I do a 5.4 release.

[mikeseese]

I've been testing these changes in 5.3.2 for a month now and haven't had any issues with the features I use. My project is in the middle of a refactor so I can't test it with 5.4.1 yet; might take me a day or two to get to that.