This commit removes the external dependencies of the AppImage generation script by instead downloading them from a known (and owned by Microsoft) location: psgithub.file.core.windows.net.
This license specifically covers the additional libraries that are bundled inside the AppImage archive.
* Use icon from local repository https://github.com/PowerShell/PowerShell/pull/2027#discussion_r75960616 * Use the deb that has been generated in this build * Copyright and license https://github.com/PowerShell/PowerShell/pull/2027#discussion_r75960505 * MIT License for appimage.sh https://github.com/PowerShell/PowerShell/pull/2027#discussion_r75960505 * Full text of the MIT License is in license_thirdparty_proprietary.txt * Clarify license and clean up unused code https://github.com/PowerShell/PowerShell/pull/2027#discussion_r76104601 * Mark appimage.sh as executable