Composer legend items inherit label font settings

[jctull]

It would be nice for items in the composer legend to inherit the font properties that are used in the map canvas. This could be optional, perhaps a check item in the legend options. E.g., a point layer might have ng labels with Helvetica font size 10, italics, and purple with a yellow buffer in the map canvas. The legend item for that layer would also be size 10, italics, Helvetica and purple with a yellow buffer.