Remove version information from schema filename, remove obsolete features

[mkavulich]

Description

Because versioning is handled with GitHub tags, and we do not support multiple schema versions for a given tag, it is confusing and unnecessary to include the version number in the filename of the schema file. Therefore this PR renames
standard_names_v1_0.xsd --> standard_names.xsd, and removes the python tooling needed to resolve the schema filename based on version.

In the process of making these updates, I noticed there is a bunch of logic for very old, unsupported python versions, and some remaining logic related to kind information that was removed in #124. I removed this unnecessary logic.

Issues

Resolves #141

[gold2718]

Approving although I'm sorry to see the Python2 go, it helps to confuse the bots :)

[climbfuji]

Do you know why only Metadata-standard-names.yaml got updated, but not Metadata-standard-names.md?

[mkavulich]

@climbfuji The parse_section function in tools/write_standard_name_table.py had logic that omitted the kind attribute entirely when it wasn't included in the XML. The parse_section_for_yaml function, on the other hand, included a "kind" line even if that attribute wasn't present.

[climbfuji]

@climbfuji The parse_section function in tools/write_standard_name_table.py had logic that omitted the kind attribute entirely when it wasn't included in the XML. The parse_section_for_yaml function, on the other hand, included a "kind" line even if that attribute wasn't present.

Ahh thanks, that makes sense.