Stylistic tweaks to TSVSerialiser.

Refs #9970.
Replace Matrix::saveToString with Matrix::saveToProject.

Refs #9970.
Tidy up newMantidMatrix orphans.

Refs #9970.
Tidy up MantidUI::openMatrixWorkspace.

Refs #9970.
Replace MantidMatrix's saveToString with saveToProject.

Refs #9970.
Refactor ApplicationWindow::windowGeometryInfo.

Refs #9970.
Replace MultiLayer's saveToString with saveToProject.

Refs #9970.
Refactor Grid::saveToString.

Refs #9970.
Refactor Graph::saveScale()

Refs #9970.
Refactor Graph::saveCurves() into Graph::saveCurve()

Refs #9970.
Refactor Graph::saveMarkers()

Refs #9970.
Refactor Graph::saveToString to Graph::saveToProject.

Refs #9970.