Users are unable to use the callbacks inside `internal/ice`.
Even though we alias things like OnSelectedCandidatePairChange
are unusable since in the package they use `ice.Candidate` instead of
`ICECandidate`
Moved ice related files to internal/ice. Added ice.go and
ice_go.go files containing aliases to internal/ice. Added
internal/tools/gen/genaliasdocs.go helper script for generating the
documentation for these aliases. Dropped ice
prefix from file names in internal/ice package.
https://www.w3.org/TR/webrtc/#dom-rtciceserver has the following default
```
credentialType = "password";
```
Update our enum to match that, currently we require users to specify
password
Fixes#515
This includes a few small and closely related changes:
1. All occurrences of the build tag `+build js` have been changed to the
more precise `+build js,wasm`. This will exclude the files from being
included by third-party compilers like GopherJS, with which they are
incompatible.
2. Some files which are incompatible with JavaScript/Wasm now have the
correct build tag (`+build -js`) so they will be excluded from Wasm
builds.
3. Some configuration options which are incompatible with
JavaScript/Wasm (or at least the current bindings) will now no longer
appear in Wasm builds. This meant creating new files with new struct
definitions and the appropriate build tags.
