New Features: Window Resize, Window Snap, horizontal scroll, treeview, folderdialog, bottom Popup

[NeuralDip]

The Features that are added here in detail are:

1. Window resize:
   -this is an integration from the old work done from ghost (fixed last requests before the merge.. i think) : https://github.com/wjakob/nanogui/pull/146

• Added the HVCUrsor
• Added the bottom-right indication that a window is resizable from christophe-f8:https://github.com/mitsuba-renderer/nanogui/pull/40
• Fixed a bug when resizing windows without layout.

2. Window Snap:
   Now window can snap between themselves. This works when a window is moved and when it is resized.
3. Added Popup bottom. This is helpful in order to create Menu bars.

• Popup windows now will shift position if they hit the left or top side of the screem

4. Added possibility for a window not to move.(added m_can_move variable)
5. Changed vscrollpanel to scrollpanel. now scrolling is possible in both directions.
6. Added TreeView
7. Added FolderDialog. Based on Treeview is a simple dialog to select folders. File save and open are not planned for now.
8. Updated example1 in order to show the features.

• Please remember to add scrollpanel and teeview files in your project in VS in order for them to be linked correctly.
• For the lower right resize cursor to appear you will have to edit the files ext/glfw/src/input.c , ext/glfw/INCLUDE/glfw/glfw3.h and ext/glfw/src/win_32_window.c that belong to the glfw submodule. You will have to add

shape != GLFW_VRESIZE_CURSOR &&
shape != GLFW_VHRESIZE_CURSOR)

in the first ,
#define GLFW_VHRESIZE_CURSOR 0x00036007
in the second and
else if (shape == GLFW_VHRESIZE_CURSOR) id = OCR_SIZENWSE;.
in the last.

P.S.I know this commit does not follow all the contributing rules, Unfortunately, me too, i don't have a lot of time to dedicate to this, i just share the code i use for my projects. In case you don't wish to go through it, then i would leave it here just in case someone wishes to take it and complete the task.
best Regards.