Allow centering symbols in measures and on notes
See discussion started at https://musescore.org/en/node/289621#comment-921655.
Symbols need to be able to be centered on measures. This will allow items like measure repeats to be centered on a measure then adjusted on the Y axis to.
There needs to be a generic symbol control that will allow centering symbols above a measure (like measure repeats) or above the note like the symbol identified as "Divide measure tremolo by 3" for example as is the current default.
Allowing attaching symbols centered on a barline would also be nice, especially in the case of two-measure repeats.