.NET 7.0 and Bootstrap 5

[plbonneville]

• Updated the projects to .NET 7.0
• Updated the NuGet packages to .NET 7.0
• Updated Bootstrap from version 4.3.1 to version 5.1.0
• Updated style where appropriate to leverage Bootstrap 5

[plbonneville]

Might be a good idea to also bump-up the version in templatepack.csproj.

[stavroskasidis]

Thank you for your contribution