Fix and extend meter export

[th-we]

Changes to previous behavior for this example:

• Hides time signature in bar 1
• Writes a time signature for bar 2 (even though it doesn't change, but it's repeated)
• Writes "cut" symbol for bar 5 (was not recognized as such before)
• Writes a time signature for bars 5 and 6 (even though it remains 2/2)
• Exports compound time signatures in bar 7