SciDAVis - Improvements SVN-temp

In contrast to SciDAVis 0.1.x, global decimal separator preference is never
used for this (i.e, "use custom decimal separator" is always assumed); and
the default locale used for ASCII import is "C". Rationale: Most applications
and programming languages use "C" conventions for dumping numbers, not
localized strings.
- Added "numeric data" option in place of "use custom decimal separator".
By default, this option is disabled, giving the same behaviour as in
SciDAVis 0.2.0 (so you get a faithful replica of the file, even if it
contains 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).