Setting horizontalSizing/verticalSizing on a FlexLayoutProxy was
dispatching update-layout-child instead of update-layout, so the
frame's auto-sizing (hug content) was never triggered even though
the getter read back the value correctly.
Also restricts accepted values to #{:fix :auto} (matching shape.cljs)
since frames cannot use :fill, and fixes a copy-paste error that
reported :horizontalPadding instead of :horizontalSizing in error messages.
Signed-off-by: Andrey Antukh <niwi@niwi.nz>
The main idea behind this, is move all plugin related stuff from
app.main.data.plugins into app.plugins.* and make them more consistent.
Also the intention that put all plugins related state under specific
prefix on the state.
