`public` attribute handling in multi-config scenario

[Qwaz]

If the value of public attribute is different among configurations, we are going to use any with exceptional rejection strategy.

As public attribute has a default value of "false", setting public on any "true" value looks natural. However, if Soma detects explicit settings of both (i.e. explicit "true" and "false") we should reject it as it is apparently a bad configuration.