v1.5-future-preview1

This release includes several changes that have not yet been merged into master in order to let people try them out. The key changes are:

• Running OmniSharp on an embedded Mono runtime. This should greatly increase the breadth of Linux distributions that the extension will work with. Note that this only affects OmniSharp, which provides editing features like auto complete, find all references, rename, etc. The debugger is still limited to a smaller set of Linux distributions.
• Initial support for MSBuild-based .NET Core projects. There is still a great deal of work to support the new MSBuild-based .NET Core projects properly, but OmniSharp can now understand and load them properly.
• Better performance via concurrent communication with OmniSharp. Previously, communication with the OmniSharp server was handled serially. This meant that long-running operations (such as gathering all diagnostics for a project) could cause the entire system to wait. Now communication is better-prioritized: high priority work (such as buffer changes due to typing) are handled serially and long-running operations are allowed to run and respond when they're ready.
• Initial C# 7 support. OmniSharp has been updated to the latest Roslyn 2.0.0 bits, enabling C# 7.