This prepares to have both not anymore in the pipe-separated tag list.
However, this patch makes the solution appear twice in the nvts table
for the time being. Just like solution_type already.

This patch expects that there is a additional column in the nvt
table "solution." A migrator is forthcoming, for testing this can
be done:
ALTER TABLE IF EXISTS nvts ADD COLUMN solution text;

This one adds the solution.

This allows to access solution and solution_type when
iterating over results.

This also serves get_info for type NVT.
The explicit elements "solution" and "solution_type" are appended
to the pipe-separated tag element of the nvt.
This is a temporary solution until the XML structure of a NVT
has explicit solution and solution_type elements. Once
that is established, we don't need to append them to the tags anymore.

This appends the explicit stored solution and solutions_type
to the pipe-separated tag element. Once the solution and
solution_type are explicit elements of the XML definition,
this can be dropped.

Since solution and solution_type are now appended
to the tag string for API compaitibility where the respective XML
is created, we do not need to store them into the tag in the database
anymmore!