Soldermask panel doesn't scale well

Description

It appears that we force linebreaks in the description of the Soldermask/past setup panel.

I think the positive/negative text probably belongs as a tooltip. We also have notes on the top and bottom of this panel.

Steps to reproduce

1. Adjust default font size on Linux
2. Run pcbnew

KiCad Version

Application: Pcbnew

Version: (5.99.0-2694-gc4de3c8f1-dirty), debug build

Libraries:
	wxWidgets 3.0.5
	libcurl/7.68.0 OpenSSL/1.1.1g zlib/1.2.11 brotli/1.0.7 libidn2/2.3.0 libpsl/0.21.0 (+libidn2/2.3.0) libssh2/1.8.0 nghttp2/1.41.0 librtmp/2.3

Platform: Linux 5.7.0-2-amd64 x86_64, 64 bit, Little endian, wxGTK

Build Info:
	Date: Aug 12 2020 13:54:44
	wxWidgets: 3.0.5 (wchar_t,wx containers,compatible with 2.8) GTK+ 3.24
	Boost: 1.71.0
	OCC: 7.3.0
	Curl: 7.68.0
	ngspice: 32
	Compiler: GCC 9.3.0 with C++ ABI 1013

Build settings:
	KICAD_SCRIPTING=ON
	KICAD_SCRIPTING_MODULES=ON
	KICAD_SCRIPTING_PYTHON3=ON
	KICAD_SCRIPTING_WXPYTHON=ON
	KICAD_SCRIPTING_WXPYTHON_PHOENIX=ON
	KICAD_SCRIPTING_ACTION_MENU=ON
	BUILD_GITHUB_PLUGIN=ON
	KICAD_USE_OCC=ON
	KICAD_SPICE=ON
	KICAD_STDLIB_DEBUG=ON
	KICAD_SANITIZE=OFF