Stabilize SourceForge mirror, Cmdline export fixes and modpack format

[HebaruSan]

Motivation

Since #4172 added support for SourceForge krefs and KSP-CKAN/KSP2-NetKAN#183 indexed one, KSP2 mod KSRe's download property has been switching from one mirror host to another at every inflation:

Changes

Now Netkan always uses the psychz mirror for SourceForge downloads since it is in a central, densely populated location.

https://sourceforge.net/p/forge/documentation/Mirrors/

Side fixes

While working on the above, a few additional small things came up:

• The SHA1 and SHA256 download hashes aren't considered in CkanModule.MetadataEqual, but the install_size is. This could mean that a user would not be prompted to reinstall a re-uploaded mod if the new ZIP had the same file size but different hashes.
  Now the hashes are also checked.
• ckan list --export had several quirks:
  • The --help info said it accepts a format parameter without saying what the allowed values were.
    Now it mentions the allowed values.
  • There was no way to export a .ckan modpack file even though this is the most popular format.
    Now --export ckan does this.
  • The csv and tsv formats were missing three columns because we were using a format string that had to be updated every time a column was updated, and it wasn't.
    Now we use string.Join instead and it works better.