+ marked expression package as optional for spring-context

Author: Costin Leau

org.springframework.context/template.mf

@@ -28,7 +28,7 @@ Import-Template:
  org.springframework.aop.*;version="[3.0.0, 3.0.1)",
  org.springframework.beans.*;version="[3.0.0, 3.0.1)",
  org.springframework.core.*;version="[3.0.0, 3.0.1)",
- org.springframework.expression.*;version="[3.0.0, 3.0.1)",
+ org.springframework.expression.*;version="[3.0.0, 3.0.1)";resolution:=optional,
  org.springframework.instrument.*;version="[3.0.0, 3.0.1)";resolution:=optional,
  org.springframework.metadata.*;version="[3.0.0, 3.0.1)",
  org.springframework.util.*;version="[3.0.0, 3.0.1)"