Added support for RTL languages, correct list indentation

[werksjan]

RTL Languages

I added

@property(nonatomic) NSTextAlignment textAlignment;

to the BPDisplaySettings, so the system's default (Natural) may be overridden in case the content is known to contain a right-to-left language on a left-to-right device.

The setting get's interpreted when styling the paragraphs in the BPAttributedStringConverter and defaults to NSTextAlignmentNatural, the system default.

Correct list indentation

When list items run over more than one line, the broken lines should be indented so they start where the first line starts; after the bullet and the space.

For that to work, instead of inserting tab characters before the list item to match the level, I insert the zero-width character for all levels and apply the correct indentations for the level to the paragraph style.

As the bullet uses a monospace font and (afais) cannot be configured, this should work for any settings.