Schema fixes corresponding with spec

[davedoesdev]

See https://github.com/ietf-wg-cellar/matroska-specification/blob/master/ebml_matroska.xml

• Slices maxver is 0 https://github.com/ietf-wg-cellar/matroska-specification/commit/848058c889a6b6f14eb0930c74fa2abe83e715a6

See https://github.com/ietf-wg-cellar/ebml-specification/blob/master/ebml.xml

• CRC-32 description missing ending period.
• EBMLMaxIDLength range missing ">="
• EBMLMaxSizeLength should be "not 0"
• Deprecated Signature-related elements are at level 2 (SignatureSlot at level 1) (see https://github.com/ietf-wg-cellar/ebml-specification/issues/391#issuecomment-759386201)
• EBML element is maxOccurs 1 so can't be multiple

[davedoesdev]

FYI I'm automatically generating schema here: https://github.com/davedoesdev/matroska-schema

[kmare]

Works fine for me.