Fix warning about invalid 'RootNamespace',

by removing the invalid hyphen character, and setting the correct namespace (Ocotkit.Tests).
Fix warning about missing DefaultLanguage,

by including the correct DefaultLanguage setting the csproj.
Remove old package references from Octokit,

because they're not referenced from the project anymore.
Put back 'developmentDependency=true' packages intp packages.config,

because they're development dependencies.