Different class definitions with the same name CBufferDatabase

The class CBufferDatabase has two different definitions in the designer and extras. The problem is that they have subtle differences (m_ChannelLookupIndices/m_ChannelLookupIdxs, ESignalDisplayMode m_displayMode / CIdentifier m_displayMode and associated methods). When loading plugins, the linker selects one of the implementations and this creates subtle bugs very difficult to find.... In the gtk3 rewrite, this makes the signal display plugin to show only the current update chunk instead of the whole signal.

More globally I do not understand why there are (visualization or any) plugins (advanced and simple) in the designer.... For now, I fixed the problem by copying the designer version into extras, but this is just to avoid changing the gtk3 branch too much. This way, there are still two implementation but they remain coherent.

This cannot be the right fix though. My preferred solution would be to merge designer and extras plugins...