Persist previously selected segment after reloading a file

[SingleCopy]

Persist the previous segment name and check if it exists when reloading a file. If it exists, it will use that as the selected segment rather than defaulting to the first segment in the array. This is helpful when working on cartridge games and you've had to do reload after making a change.

Additional changes.

• Removed C64DebuggerPluginShowPic.h and C64DebuggerPluginShowPic.cpp from the .vcxproj as these files are missing
• CViewDisassembly.cpp: Add a null check for the currentSegment as this has sometimes caused a crash when debugging