DDSOPCU — Improve readability of a number of figures

Figure 9.2, which describes the mapping of DDS primitive types to OPC UA is hard to read. We should break the figure into different class diagrams. For example, we could create one diagram for primitive types, one diagram for floating point types, and one diagram for boolean, char, and byte types.

Also, Figures should be in black and white when possible; e.g., Figures 7.3, 8.1 and 9.1 could be made black and white.

Fix figures with readability issues

The resolution of this issue replaces existing figures with readability issues with new images.