Added option to store multiple literals inside 1 Ifc text object.
If multiple literals share the same `BoxAlignment` then only the first one will be displayed in viewport
to prevent visual clutter (although added small asterisk symbol to indicate that there are still multiple literals).
Added option for aggregated text annotations. Example - "door-tag" symbol.
If you create text, specify "door-tag" symbol in EPset_Annotation.Symbol
\and add two literals to it then they'll automatically will fit to that door-tag in the svg drawing
(https://i.imgur.com/OXaIlWe.png).
The way it works - you define symbol in symbols.svg (or in your own symbols svg file)
and then add the `<text>` fields where text from literals will fit right in.
The imporant note: `<text>` tag must have attribute `data-type="text-template"` for it to work.
For example: `<text text-anchor="middle" dominant-baseline="middle" data-type="text-template"></text>`
TestExportTextLiteralAttributes and TestImportTextAttributes was failing because now we're assuming that BoxAlignment will have 1 of values from the list below and not "BoxAlignment"
"top-left", "top-middle", "top-right", "middle-left", "center", "middle-right", "bottom-left", "bottom-middle", "bottom-right"
Dion Moult
