Examples: Comments, Demo: Log early out, TODO. (#1553)

Comments, changelog

Changelog formatting update, Todo, comments. Tweak Child demo. Shuffle some code in NavUpdate().

Nav: When entering into a NavFlattened child we only consider the visible items for scoring (note that this only work assuming the NavFlattened child window has interactive items). Fixes accidentally hoping into a NavFlattened child. (#767)

Nav: NavFlattened: Fixed navigation miscrolling parent window when the current window is scrolling enough to keep the item in view. Fix feature added in e11610d6, typically affect large navigation steps (used by PageUp/PageDown). + comments (#787)

Internals: Added BeginDragDropTooltip() internal function to convey semantic (drag and drop tooltip doesn't get clipped within display boundaries). Revert part of 3218666. (#1739, #143).

Added ImGuiDragDropFlags_AcceptNoPreviewTooltip flag to disable drag source tooltip from the target site (#143)

Internals: Selectable: Renamed variables. Todo update.

Missing examples changelog bits and todo list

ImVector: added erase(it first, it last) helper. Added erase_unsorted(it) helper. + todo fixes/additions

Comments + Internals: Selectable: decoupled internal flags and removed their menu / menu-item semantic as upcoming changes are requiring more flexibility.

Version 1.61 + todo additions

Merge branch 'data_types' ...

# Conflicts:
#	CHANGELOG.txt
#	imgui.cpp

TODO list update + Changelog and comments for #1803.

Moved DragScalar, InputScalar, SliderScalar to imgui.h as well as ImGuiDataType (#320, #643, #708, #1011)

Settings: Added LoadIniSettingsFromDisk(), LoadIniSettingsFromMemory(), SaveIniSettingsToDisk(), SaveIniSettingsToMemory(), io.WantSaveIniSettings. (#923, #993)

DragInt: Patch old format strings to replace %f by %d when using the DragInt() entry point. (#320, #643, #708, #1011)

Documentation bits. Misc comments.

Comments about io.WantCapture flags + todo entries.

Demo: Added more complete Combo demo. (#1658)

Nav: Track nav input source more generally (gamepad vs keyboard) (#787) + update todos and demo tweaks

Update TODO list, minor fix in Readme, comments, Clang -Weverything warning fix in imgui_draw.cpp under Windows.

Misc comments, todos + reintroduced removed ImGuiCol defines under !IMGUI_DISABLE_OBSOLETE_FUNCTIONS wrap.

Font: Fixed MergeMode adding duplicate glyphs data instead of reusing existing (broken by 072d6d8)

Nav: Comments, guides.

Nav: SetItemDefaultFocus() doesn't make the navigation cursorr highlight visible. Renamed NavInitResultExplicit to NavInitRequestFromMove. (#787)

Nav: Comments (#787)

Nav: Child window is restored on focus when returning to layer 0 or refocusing. This is a little experimental and potentially error-prone right now. (#787, vaguely relate to ~#727) Ideally we should maintain a non-sorted last-focused list that include childs windows.

Nav: Tweak code to be easier to follow + updated todo list after clarifying an issue.

Merge branch 'master' into navigation