Move magic commands from Kernel.csproj to Jupyter.csproj

[cgranade]

Is your feature request related to a problem? Please describe.
Many magic commands are currently implemented in Kernel.csproj, which is not exposed by any library NuGet packages, but rather only as part of the tool package. This prevents external programs that depend on IQ# as a library from using any functionality provided by these magic commands.

Describe the solution you'd like
The implementation of these magic commands should be made available in the Microsoft.Quantum.IQSharp.Jupyter package by moving the relevant C# files from Kernel.csproj to Jupyter.csproj.