Compound units should accept an SI modifier on each component

[VisLab]

HED 8.5.0 allows SI modifiers on each component of a compound unit. Speed/3 cm-per-us (centimeters per microsecond) is valid because cm and us are each a modified symbol. hed-javascript currently rejects it.

Current behavior: when a unit has SIUnit, hed-javascript prepends each modifier to the whole unit string. For m-per-s this produces km-per-s, mm-per-s, and so on, which happens to accept some valid forms but rejects any form with a modifier on the second component.

Expected behavior: for a unit whose name contains -per- or ^, split the annotated unit on -per- and match each component against the schema component, allowing one SI symbol modifier in front of each. Exponents stay attached to their component.

Examples:

• valid: Speed/3 cm-per-us, Speed/3 km-per-s, Acceleration/2 mm-per-s^2, Volume/2 mm^3
• invalid: Speed/3 kmm-per-s (two modifiers), Speed/3 m-per-sec (not a symbol), Speed/3 m-per-S (wrong case)

Where: src/schema/entries.js, class SchemaUnit (constructor and validateUnit).

Tests: hed-tests case units-invalid-compound-units (commit e3fc564) covers this; add the same strings to tests/jsonTestData/tagParserTests.data.js.

Same change is needed in hed-typescript (src/schema/entries/unit.ts).