[RFR] : some refactor on #define #else #endif (add comments)

[RMV] : the directive USE_IMGUI_TABLE is removed, so cant be disabled. since ImGui v1.80 is released with the support of ImGuiTable in master, now ImGuiTable is in base
[ADD] : add a define 'DateTimeFormat' for customize the date field. see strftime func in <ctime> for customize it. default is "%Y/%m/%d %H:%M:%S" who give 2021:01:22 11:47:10

Author: aiekick