reg.exe: Allow single starting slash, error on double (For Remote)
reg.exe: Add path_get_key() to remove boilerplate
reg.exe: Add wchar/type conversion functions
reg.exe: Add internal error string
reg.exe: Add wchar/raw data conversion functions
reg.exe: Implement query functionality
reg.exe: Clean up reg_add

Adds defaults and checks
reg.exe: Clean up reg_delete