Change requirements tagging

[jyutzler]

Per Scott Simmons:

Requirements: per TC guidance, requirement numbers are now persistent. GeoPackage uses a custom block type that automatically sequentially numbers requirements. These will need to have fixed numbering going forward, so any requirements deleted in 1.2 will need to be “skipped” and inserted requirements come from the end of the list of available sequential numbers. Our new Asciidoc standard template has a method to store requirements each in a separate file. However, for GeoPackage I can give you a new block definition style (based on an Example) that will allow cross-referencing and compile nicely. See below:

[[r1]]
[caption=""]
.Requirement 1
====
requirement text, blah blah blah
====

This will require some manual work but we can do it while retaining existing requirement numbers.

[jyutzler]

One side-effect of this change is that requirements numbers will go back to what they were in 1.1. Before this fix, the requirements numbers in the extensions were different. New requirements numbers will be added to new sections - Attributes and the elevation extension.