default profile activation should consider available system and user properties

As discussed in my open PR, my use case is to compare between environment variables e.g.:

<activation>
  <property>
    <name>env.FOO</name>
    <value>${env.BAR}</value>
  </property>
</activation>

Limiting the interpolation to user/system properties means that there is no mindf*ck resulting from profile activation order, etc., and keeps this request nonthreatening.