Travis: Use XCode 9.3 / macOS 10.13 for osx/iphone builds

Update classref and docs, fix missing parameters' name

Fixed colour region calculation for the first line, issue 18104

NetworkedMultiplayerEnet: Add disconnecting/kicking peers

Implement Input.set_default_cursor_shape to change the default shape

Closes #18043

CoreAudio: Fix iphone build after audio device refactor (#17742)

We disabled them due to Travis having big infrastructure issues for osx builds,
but it seems to be back under control now.

LineEdit placeholder alignment, content margins, and overflow bugs

[DOCS] Navigation & Navigation2D

Add support for radio-looking items with icon

Allow set_custom_mouse_cursor to use same cursor(image) with different shapes

WASAPI audio driver compile fix on mingw

Make Button not emit press when container is scrolled

Made Node.print_tree() print prettily

LineEdit doesn't correctly uses style margins nor use placeholders
width correctly, causing multiple rendering bugs.

Add new transform tutorial to the appropriate classes

Corrected area overlap cleaning

Fix of RigidBody's configuration warning for Z axis

Resolves Incorrect Quaternion Conversion

Fix custom cursor when it's hidden

Drag to Rearrange Editor Docks

Letting users of `PopupMenu` use them. `OptionButton` was one of those interested and is updated in this commit.

Fixes #18063.

[DOCS] SceneTree

Fixed bug #17929. Inconsistent sort in file manager.

Fixed colour regions and added local colour region cache

This fixes the problem described in #13996 in a proper way.

This also adds "deadzone" property to ScrollContainer. It can be used
on mobile, where taps are not as precise as mouse clicks. Player could
slightly move their finger when tapping, in which case we still want
the button to be pressed rather than the container to be scrolled.

[Linux] Ensures that the custom cursor will be used when changing to
MOUSE_MODE_VISIBLE. Fix #3086

[Windows] Fix cursor flickering when MOUSE_MODE_HIDDEN.

[Mac] Fix possible cursor flicker when MOUSE_MODE_HIDDEN.