Expose the function to start the API wrapper process on Linux

[Unsanctioned]

Makes startProcess() public instead of waiting until init() is called.

Deprecates the path argument to Steamwrapper.init(). Linux users should switch to call startProcess(path) prior to init(). Passing a path to init() is still supported, but will be removed in a future version.

[Ventero]

Very nice, thanks!

I'm also planning to remove useCrashHandler, as it never really worked anyway (at least for me, but maybe I'm just using it incorrectly ...). I guess when I do that, we can also remove the path argument and do a major version bump.

[Ventero]

(Cherry-picked this commit.)