Reduce number of specific variants of common sub-value parameters in next generation command line interface

Some of the new command line interface's parameters appear redundant - it will make the interface much easier to use if parameters controlling various operations that occur in different contexts, like image export, were re-used rather than each context having its own version.

e.g. --structureimagewidth does the same thing for structure image exports as --width when exporting alignment images.. why not just have --width for both instead ?