Use better icons for data streams.

Change-Id: I57064ff251a560b71aaf1846a9d7cd9105f938df
Rework data streams to be more like file links (ScAreaLink).

By inheriting from sfx2::SvBaseLink and storing in sfx2::LinkManager we can
have more data streams and see / remove them in Edit -> Links... dialog.
Also rename to DataStream to avoid confusion.

Change-Id: I9c3b89020324af7be082f9e6e1cd479aeb72fe81
Import data streams - reuse infrastructure for ScAreaLink.

Change-Id: I18db991d2e8e665d5e4ca778344993e79772ccd5
export data streams; pretend to be an area link

Fix ScXMLExport::GetAreaLinks to not use UNO, so we can hack DataStreams
into ScMyAreaLinksContainer.
We need to connect them to cells for export / import - that does not make
sense for DataStream without any attached range. We use an arbitrary one.
But you might remove it, if you create another ScAreaLink / DataStream
with the same range, without knowing about it.

Maybe it wouldn't be that bad to let DataStream inherit from ScAreaLink.

Change-Id: I5b85a9329ba1ca46fb2893b54fe5161d2fb22f47
Allow to edit data stream from Edit-> Links... dialog.

Change-Id: Ibb456da55f04c39ddb7b58eb71ca488cf209edb5
Let's use ScRefreshTimer for data streams instead of our own thread.

As was the original idea, for some reason abandoned, and as ScAreaLink does.

The main advantage is that ImportData() is not called anymore with
invalid mpScDocument (when we close it).
There is surely something going on with SolarMutex and it just works better.
We do not need to use our own SolarMutexGuard.

Change-Id: I09256a18ffa14606fc8e06b968016bbc0562a6fa
datastreams: for security, ask before executing a script when importing

Change-Id: I76a11dae2569eb7e0c791c9f1fb20626c4ff7528
datastreams: Simplify code for importing CSV data.

The code is copied and simplified from sc/source/ui/docshell/impex.cxx.

Change-Id: I15a426a16c4f2ba659af86492c1b2e4ba879d8b6
datastreams: No need to disable undo. We do not add undo actions.

Also fixes memory leak, because EnableUndo()
was called from Document's destructor.

Change-Id: I637ff62bde6f8c3238238323e6e4a5a5d2b81881
fix memory leak

Change-Id: Ic84ace8ac3aa52009f43aafe78283730f97881f2
make data streams an experimental feature

Change-Id: I674b86a6e1c1c0b162c159747b6900ce438ab095