We need to add the export macro to TSVSerialiser's class definition and
update the namespaces

This is so that it is accessible via widgets as well.

While we're here this might as well be done.

If the global "autoscale" property is set to off, don't autoscale the
color bar axis in color fill plots. If it is on, autoscale as normal.

This is the property under View > Preferences > 2D Plots > Autoscale.
Must propagate it through to the Spectrogram with the color bar axis
so that it can use this property.

Use case: color fill maps of live data with user-set color maps should not
reset the scale every time new data comes in

Since v3.2 and prior crash when dealing with spectrograms, we don't have
to worry about compatibility, so we're allowed to deal with this a
little more simply.

If the spectrogram's based off a matrix, we specify the matrix by its
name. If the spectrogram's based off a workspace, we specify the
workspace by its name.

Load and save accordingly.

The matrix a spectrogram was meant to be representing was not being
saved into the project files. This has now been resolved. However, this
is not being saved in previous versions of Mantid (which crash when
dealing with spectrograms apparently).

Refs #9970.

Refs #9970.

Refs #9970.

Spectrogram is not an MdiSubwindow, so it doesn't need this interface,
as it's not going to be serialised directly. It's explicitly
serialised/deserialised by the graph that owns it. So we can ditch the
official interface and just use simplified methods similar to the
interface.

Refs #9970.

This commit tidies up a few rough edges that I had left behind.

Refs #9970.

This commit add basic support for parsing spectrogram sections and
loading them into projects properly. Not all sections are supported yet.
<ColorBar> and <ColorMap> are notably unsupported. They shouldn't be too
difficult to add later on though.

Refs #9970

Refs #9970

The caching in the framework means that the performance is now
acceptable in both cases.
Refs #9435

Refs #9319

This only applies to those created directly from a workspace.
Refs #9319

It also doesn't use any overlays.
Refs #9319

Refs #9319