While "set" is a tad strong (there's just the one component for now), I
had missed the changes when adding ECS systems. Fixes the segfault at
the end of demo1 (ie, when any center text is printed).
Instead of creating new entities for the text views. This approximately
halves the number of entities required to display flowed text, but also
tests the ability to have an entity in multiple hierarchies (the goal of
the ECS component and system changes).
There's now a main ecs.h file that includes the sub-system headers,
removing the need to explicitly include several header files, but the
sub-systems are a less cluttered.
Font cannot be overridden yet, but script attributes (language, script
type, direction) and features can be set at all three levels in a
passage. Attributes on the root level act as defaults for the paragraph
and word levels, and paragraph attributes act as defaults for the word
level.
And add a function to process a passage into a set of views with glyphs.
The views can be flowed: they have flow gravity and their sizes set to
contain all the glyphs within each view (nominally, words). Nothing is
tested yet, and font rendering is currently broken completely.
