SciDAVis 0.2.1 released

This is the first bugfix release in the 0.2 series. Most importantly, saving project files containing fit/function curves works again. This bug also affects version 0.1.4; but since 0.2.1 should fix the critical issues in 0.2.0, users are assumed to upgrade to this release and a bugfix release for the 0.1 branch will be made only if requested.

Other fixes and updates include:
- fixed opening of backup copy on discovery of a corrupt project file
- Spanish translation update by Mauricio Troviano
- fixed several regressions introduced by the table/matrix rewrites in 0.2.0
- added per mille and per ten thousand signs to SymbolDialog
- compatibility problems between SIP versions triggers a warning instead of a
crash (happens sometimes when SIP version at runtime differs from the one
used at compile time)

There's a small update to the dialog for importing ASCII files with numeric data: The global decimal separator isn't used any more (as it was in SciDAVis 0.1.x); effectively, the old option "use custom decimal separator" is always set. Most applications and programming languages use "C" conventions for exporting numbers, so defaulting to "C" makes more sense than defaulting to the format chosen for display. In place of the custom decimal separator setting, a new "numeric data" option has been added. By default, this option is disabled, giving the same behaviour as in SciDAVis 0.2.0 (which makes it possible to import files containing text or date/time data). By enabling it, you get the same behaviour as in SciDAVis 0.1.x, which is useful if you're working with lots of numeric data (assumed to be a common use case).