Reset Text to Style button in Inspector works only on single element

Ubuntu 14.04, GIT commit: 6b554a9

1) add two staff text elements to score, using text toolbar to enter custom formatting
2) select both
3) Inspector / Reset Text to Style

Result: only one element is affected. This limits the usefulness of this greatly - there is already a similar button in text Properties that affects only a single element. This seems simple - loop through el() rather than operate only on element().

There is another limitation in the usefulness of this button: it only resets formatting changes made using the text toolbar, not using Text Properties dialog. That's because we don't actually change the style, only the text (stripping out the markup).

It's possible both of these limitations were deliberate, but they render the button not useful for the main thing I was hoping it would be useful for.

PR forthcoming to address both of these limitations.