On Windows, removes the hard dependency on PowerShell and MS Office (or LibreOffice) to parse XLS files.
On Windows with default settings, PowerShell might have a strict security policy against apps running arbitrary scripts. Also, accessing MS Office via PowerShell is not as reliable as I previously assumed.
On Linux, removes the hard dependency on LibreOffice to parse XLS files.
When packaged with Flatpak, this caused a lot of issues where ikoOSKAR tried to access LibreOffice's commandline interface, but was unsuccessful due to the sandboxing policies of Flatpak.
Parsing XLS files in MultiImport is a lot faster now, since it doesn't rely on custom scripts and big bloated office suites anymore. All the parsing logic is baked in.
Added support for XLSX files in MultiImport.
Improved the recognition of standard XLS(X) format, and added flexibility to non-standard XLS(X) format.
Resolves #28