The terminal's Shell path setting was split with POSIX rules, where a backslash escapes the next character, so C:\Windows\system32\cmd.exe reached the backend as C:Windowssystem32cmd.exe and every new terminal failed to start. On Windows a backslash is now a path separator, and an unquoted path up to its .exe/.cmd/.bat/.com is the program even with spaces; paths picked from the Installed Shells menu or Browse are quoted when they contain whitespace. This was the only place the setting is parsed.
Fixes#1327
