Fix mixture of tabs and spaces
The active state is now more carefully managed

By default if po2moz runs it it will default to marking as active. With
po2mozlang you have a command line option.
If a unit is fuzzy revert to empty string

This way the .lang store will use Source in its output but will not mark it
with the {ok} flag.
Test correct working of {ok} marker

The {ok} marker indicates a string that is the same as source but is still
translated.
Handle multiline comments

Ensure we preserve multiline comment layout