Fix#3951. When an Excel sheet is protected, even when sorting is explicitly allowed without a password, sorts are permitted only on "protected ranges" within the sheet. PhpSpreadsheet already supports protected ranges, and only minor tinkering is necessary for that (e.g. the protected range can have, but does not require, a password). The more important part of this change is documenting the far-from-intuitive way that Excel handles this. To that end, documentation is updated, and a new sample is added.
A new class, `Worksheet\ProtectedRange` is added in place of the string array which had been used. `Worksheet::getProtectedCells` is deprecated in favor of the new `Worksheet::getProtectedCellRanges`.
The samples have become unwieldy when running them from a browser. In particular, the drop-down lists are fixed size with no scrolling, and many of them are now just too large. I have moved all the Calculation samples up a level, and broken several categories (Basic, Chart, DateTime, Engineering, Financial, and Reader) into several pieces.
Convert-Online (now found in the Engineering category) had a number of different problems which are now resolved. It is the only member with any significant code change.
oleibman