Change all of our NuGet metadata to use license expressions (OSOE-852)

[Piedone]

NuGet license expressions make the type of license of a package readily apparent, and help with license checkers, and thus getting adoption for our packages. See https://github.com/aaubry/YamlDotNet/pull/903 for an example of such a change but that's about nuspec files.

So, since all of our packages use a BSD-3-Clause license anyway, let's change all of our open-source csprojs from this:

<PackageLicenseFile>License.md</PackageLicenseFile>

To this:

<PackageLicenseExpression>BSD-3-Clause</PackageLicenseExpression>

Or if we have nuspec files then to this:

<license type="expression">BSD-3-Clause</license>

• [x] Test the change proposed above with an alpha release of any single-package project first.
• [x] Change all NuGet-published projects of ours.
• [x] Check if lines like <None Include="License.md" Pack="true" PackagePath="" /> can be removed from csprojs too; most possibly yes, then remove them.
• [x] Update our documentation.

Jira issue

[AydinE]

Have created a PR the only thing I am not sure on is which documentations need to be updated to reflect these changes.

[Piedone]

This wiki page: https://lombiq.atlassian.net/wiki/spaces/DEV/pages/2609840133/Preparing+a+.NET+project+to+be+published+on+NuGet

[Piedone]

Can you please link to where you tested this?

Test the change proposed above with an alpha release of any single-package project first.

[AydinE]

Oh I put that under the description of the PR: https://github.com/Lombiq/Open-Source-Orchard-Core-Extensions/pull/789#issue-2343902880

[Piedone]

OK, great!