Remove github release creation from build script

Fix nuget API key

Updated with xbuild bootstrapper for *nix.

Add $Configuration$ replacement parameter to nuget pack

Explicitly build build.proj since there may be more projects at the root

Added ability to override the default automatic version to use for bu…

…ilding nuget packages

Use simple package versioning in our case.

Updated to latest SemanticGit

Added sample AppVeyor config

Release on GitHub should match the repo tag