Fix exact number filters, multi-cell BLOB paste and export write errors - #4245

Pasting a single cell already stores binary data as a BLOB, but pasting
several cells went through setData(), which always stores the value as
text. Binary data copied from a BLOB cell ended up as corrupt TEXT in the
destination cells, which other applications can not read back.

Use setTypedData() for each cell, like the single cell cases do, and
keep the editability check that setData() did.

Add test-paste, which copies and pastes cells through the key shortcuts
of the table view.

Fixes the multi-cell case of sqlitebrowser#3307

When the disk is full, write() first writes as much as still fits and
returns the smaller number. The JSON export ignored this, so it reported
success and left a truncated file. The CSV export did not notice a
failure to write the last chunk of data either, because a QTextStream
only writes it when it is flushed, which happened after the last check.

Check the result of writing the JSON document and flush the CSV stream
before checking it. Don't commit the QSaveFile when something went
wrong, because that replaced an existing file with the incomplete one.

Add writeAll() and flushStream() for this and test them with a device
that behaves like a full disk.

Fixes sqlitebrowser#3243