hide increase/decrease buttons from nk_property_*()

Using:
`nk_edit_string_zero_terminated()`
I got a compact widget and node windows:
https://github.com/efa/PowerBudget/blob/main/PowerBudgetGUI.png
but cannot get to right update for double values.

So I changed to:
`nk_property_double()`
now the update of double values work, but the widget has the increase/decrase arrow that waste space.
I had to increase the size from 50 to 70 pixel for each value entry, so from 256 to 316 of node windows.
I tryed to use "###name" (# autohash, ## skip label, ### skip label and button)
and disabling /* execute right/left button */ code in:
`nk_do_property()`
on `name[1]=='#'`, but the space is still reserved and left blank.

I also tryed to comment the:
```
/* left decrement button */
left.h = font->height/2;
...
```
calculated fill in the same function, but wont work.

Is there a method to hide increase/decrease button to save space?

Start with nk_property_double() and the nk_do_property() layout and button-handling paths mentioned in the report. Trace how the increase/decrease controls reserve width even when their rendering is disabled, then verify that a property can hide both buttons without leaving blank space and still update double values correctly.

Written by the indexing model from the issue text.