Upgrade Cake to 2.0.0 and use Cake.Tool so we can build on all platforms

[CharliePoole]

With 2.0.0, Cake.Tool is the only available runner so both changes will be made simultaneously.

[CharliePoole]

Usage note: with this new release, all options go directly to cake without being processed by the bootstrap script. Therefore, the options must be in cake format. So, rather than build -t Test, use build --target=Test.

[CharliePoole]

This issue has been resolved in version 3.13.1

The release is available on:
GitHub.
NuGet packages are also available NuGet.org and
Chocolatey Packages may be found at Chocolatey.org