SciDAVis - Improvements SVN-temp

Added .desktop files for menu entry and mime type on Linux.

- Extended search for default paths to the manual to include
a) /usr/share/doc/scidavis-<version>/
b) .../manual/index.html in addition to .../manual-<locale>/index.html

- Fixed some bugs in Plot3DDialog. Updated other deprecated uses of
setCurrentItem(int) in order to avoid similar bugs.
- Fixed floor.xpm and graph.xpm.
- Removed Qt::Tool window flag from instantiations of LineDialog, because it
caused some strange behaviour when switching workspaces. Besides, it's a modal
dialog so this flag doesn't really seem appropriate here. Strangely enough,
SymbolDialog doesn't suffer from the same problem.

Updated several screenshots and deleted some unreferenced ones. Some parts of
the manual still have to be updated (several dialogs were merged into the "Plot
details" dialog, some preferences are not described, menus and toobars have
changed etc.). If all screenshots would use the same style, this would be a
bonus (style options for the updated screenshots are described in README.style).

- Added a generic interface for import filters (AbstractImportFilter) and a
matching dialog (ImportDialog). This is supposed to improve usability (I want
to import something -> open import dialog -> see what filters are available)
and make implementing new import filter much easier.
- Implemented import of ASCII tables.

Some minor clarifications.

Removed superfluous executable bits and converted some files to unix format. Thanks to erictanguy for spotting these.

- fixed unique name generation
- fixed ordering of Column children in Table

- fixed context menu in TableView
- adjusted column- and table-test to the new framework
- fixed a crash when inserting rows into a table
(double signal connection due to copy&paste mistake)
- fixed a crash when calling Column::setColumnMode()
twice (wrong check for ownership in dtor of
AspectChildRemoveCmd)

- AbstractAspect enforces unique names among siblings.
- Removed SciDAVis::Date and SciDAVis::Time - the import filter for the legacy
file format will map them to SciDAVis::DateTime.
- Renamed "options tabs" to "control tabs" and tried to make the layout more
compact.
- Removed manual from trunk; manuals should go to /manual/<major.minor>.