MU 4.0: "keep measures on the same system" should be staff dependent

Layout elements like system break and page break are part dependent. No information needs to be passed from the score to the parts. Conversely, section breaks do need to be passed to all parts. The "keep measures on the same system" (KMOSS) element in not like the section or page breaks in that a KMOSS needs to be passed from the score to the parts and vice versa. Neither is the KMOSS like the section break, since the KMOSS may not need to be passed to all parts.

Currently, the KMOSS is associated with a measure and is passed to all parts. This can be a problem since not all parts need to know about the KMOSS and the presence of a KMOSS can cause formatting deficiencies (specifically, preventing a desired system break) in some of the parts. If the KMOSS were associated with one or more staves (in addition to a measure), then the KMOSS can be passed only to those parts which would be affected by the KMOSS. Note that the KMOSS might affect more than one staff at a particular measure and might have to be associated with multiple staves at an affected measure. (This would be done automatically by a multi-measure rests on more than one stave or manually by the user from the Palette.).