Refactor: Internals: Moved Navigation functions in imgui.cpp in their own section. DONE! (part 9) (#2036, #787)

Refactor: Internals: Moved Navigation functions in imgui.cpp in their own section. (part 8) (#2036, #787)

Refactor: Internals: Moved Navigation functions in imgui.cpp in their own section. (part 7) (#2036, #787)

Refactor: Internals: Moved Navigation functions in imgui.cpp in their own section (moved NavUpdate which would not diff properly unless empty lines were removed, hence the previous patch). (part 5) (#2036, #787)

Refactor: Internals: Removing new lines from NavUpdate solely because I couldn't find another way to get a neat diff/patch when moving it. (part 4) (#2036, #787)

Refactor: Internals: Moved Navigation functions in imgui.cpp in their own section (extracted some code out of NavUpdate()). (part 3) (#2036, #787)

Refactor: Internals: Moved Navigation functions in imgui.cpp in their own section. (part 2) (#2036, #787)

Refactor: Internals: Moved Navigation functions in imgui.cpp in their own section. (part 1) (#2036, #787)

Refactor: Moved Slider/Drag/Input functions + support DataType stuff from imgui.cpp to imgui_widgets.cpp (#2036)

Refactor: Moved ColorEdit/ColorPicker/ColorButton/etc. functions from imgui.cpp to imgui_widgets.cpp (#2036)

Refactor: Moved Button/Image/Checkbox/RadioButton/Bullet/ProgressBar functions from imgui.cpp to imgui_widgets.cpp (#2036)

Refactor: Added imgui_widgets.cpp headers to easily merge in the functions in all our branches. (#2036)

Refactor: Added empty imgui_widgets.cpp + updated project files / makefiles etc. accordingly (#2036)