First attempt to build a win32 version
Remove toolbar border
US25: Reduce the differences between Linux and Windows

- Reduce the number of changes needed between the Linux and Windows version.
- Add the example toolchain file for W64.
- Add a summary of the instructions to build the dependencies with MinGW-w64.
US25: Updated build method

- Toolchain files stripped to minimum.
- Update build guide with complete explanations and commands.
- Fix translation.
US25: Fix indentation
Fix small problems with the Windows version.

- Integrate the toolbar icons in the executable.
- Fix the storage of settings with an organization name.
- Fix some default margins that get different values in each platform.
- Move the toolbar to the top of the window.
- Add a tooltip to the layer buttons to show the EV steps relative to the least exposed image.