#270 removed checkbox and added restriction-combobox

In the Sb_stadtbildserieEditor, the checkbox for the field
interne_nutzung was removed and a checkbox for the new restrictions was
added.
 #270 set 'no restriction' as default value

If a new Stadtbildserie is created, 'no restriction' is the default value
for the nutzungseinschränkung.
 #270 added Combobox to Search

Added the Nutzungseinschränkung-ComboBox to the
Sb_StadtbildWindowSearch. The id of the selected Einschränkung is also
added to the server search.
 #270 started removal of isInternalUsageAndRenderer()

Over the next commits the method
stadtbildserieProvider.isInternalUsageAndRenderer() will be removed and
replaced with another method, which will only check if a stadtbildserie
is restricted. Therefore everywhere where isInternalUsageAndRenderer()
is used a check of isEditable() is also added.
 #270 renamed the method to isRestricted()

See previous commit.
 #270 jalopy
 #270 created the method determineRestrictionLevelForStadtbildserie()

The method determineRestrictionLevelForStadtbildserie() determines the
restriction level for a stadtbildserie. The restriction level depends on
the action tags which the user possesses. It allows the user to download
or preview stadtbilder of the serie.
 #270 use the RendererLevel instead to check restrictions

The RendererLevel is now used instead of the boolean for the
internalusage.
 #270 removed "internal usage" from GridObject

The Sb_AbstractPictureGridObject and its subclasses used "internal
usage", to determine if a preview can be shown. This is now determined
via the RestrictionLevel.
 #270 remove further occurrences of "internal usage"

In Sb_stadtbildserieAggregationRenderer the field "interner_gebrauch"
was used several times to avoid the preview or the download of images.
 #270 remove 'interner_gebrauch'

In Sb_stadtbildserieGridObject.isPreviewAllowed() use the restriction
level, instead of 'interner_gebrauch'
 #270 added a bullet point to the grid renderer

A bullet point is shown in the Sb_stadtbildserieGridRenderer, whose
color depends on the RestrictionLevel of the Stadtbildserie.
 #270 replaced the label with the bullet point

The label with the bullet point was replaced with an JXImagePanel
because there where problems with the transparency of the bullet point.
This was probably a issue with Swing, which has problems to draw two
overlapping images.
 #270 the restrictions should only depend on actionTags

The restrictions, if the preview is shown or the download is enabled,
should not depend on the fact that the editor or the renderer is open.
But they should depend solely on the actionTags, which the user
possesses.
 #270 draw the marker behind the label
 #270 set the tooltip for the bullet point
 #270 RestrictionLevel is now an internal class

The enum RestrictionLevel is now a internal class, because the
restrictions for the internal usage and the external usage were added.
 #270 cache the RestrictionLevel for a serie

The RestrictionLevel of a StadtbildSerie has to be cached, as it is
takes too long to determine it each time, especially as this is done in
the EDT. The RestrictionLevel is saved in the extension attribute
tmp_restriction_level.
 #270 surround messages with html-tags

In Sb_StadtbildPreviewImage the messages, shown to the user must be
surrounded with html-tags to wrap the text.
 #270 check if preview permission allowed before download

If the preview image is downloaded in another thread it is checked, if
the user has the right permissions. This was previously done in the EDT,
which lead to gui freezes.