SciDAVis - Improvements SVN-temp

- Update of Czech translation by Pavel Fric.

- Implemented picking of data points from Python scripts, i.e. querying the user
to select a point of a curve on a given graph layer.

- More efficient ASCII export of (large) tables.

- Clarified colormap file format.

- Fixed remaining issues with inserting columns and Qt 4.6. Closes bug #2935369.

- Fixed crash when creating a table with given Column objects.
- Fixed performance issue in Differentiation (when applied to large tables).

- Updated download page to point to the LabPlot repository for the development
version.

- Added link to API documentation of the development version.

- Webpage ported to webgen 0.5.x.

- Some pages updated. Better screenshot on index page.

- Removed outdated description of Aspect framework. Will be replaced with an API
documentation for the development version, which is easier to keep up to date.

Update of Spanish translation by Mauricio Troviano.

- Reduced memory usage during save and restore of large tables. This avoids
crashes observed on Windows for projects on the order of magnitude 100MB.
Closes bug #2897197.