[MU3] FirstSystemIndentation taking care lenght instrument labels

[njvdberg]

Resolves: https://trello.com/c/055jGzml/13-first-system-indentation-should-not-apply-where-instrument-labels-are-present

First system indentation now takes the maximum of the length of the instruments labels and the style parameter firstSystemIndentationValue. The maximum value of this parameter is now exceeded to 1000.0 which is the same maximum used in other parameters.

SectionBreak also generates a first system indentation but this can be enabled/disabled per SectionBreak.

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[chenlung]

Typo: ‘length’