Sets a name/value pair for the section with the given {@code sectionName}. If the section does not yet exist,
it will be created. If the {@code sectionName} is null or empty, the name/value pair will be placed in the
default (unnamed, empty string) section.
@param sectionName the name of the section to add the name/value pair
@param propertyName the name of the property to add
@param propertyValue the property value
Sets a name/value pair for the section with the given {@code sectionName}. If the section does not yet exist, it will be created. If the {@code sectionName} is null or empty, the name/value pair will be placed in the default (unnamed, empty string) section.
@param sectionName the name of the section to add the name/value pair @param propertyName the name of the property to add @param propertyValue the property value