XTCE12 — XTCE12-11 fix for name references did not work correctly

The resolution for XTCE12-11 turned out to have an error. The Comments section outlines the error in that issue.

Propose to correct the mistake introduced in resolving XTCE12-11

Replace the NameReferenceType simpleType in the schema with the following definition that includes a revised annotation and regular expression.

<simpleType name="NameReferenceType">
<annotation>
<documentation>Describe a reference to a named item in an XTCE instance document. The named must be of schema type NameType. All name references use a Unix style file system name format where the SpaceSystem names form a path in the SpaceSystem tree. The following characters are reserved for the path: '/', ‘..’ and ‘.’ (multiple consecutive ‘/’s are treated as one). The path portion is similar to the directory path used in file system names and the path characters have similar meaning (e.g., SimpleSat/Bus/EPDS/BatteryOne/Voltage). There are three overall forms for name references: absolute path, relative path and just the name. The first two forms are called qualified name references; the last form is called an unqualified name reference. The unqualified form refers to an item in the SpaceSystem the reference is used in. The unqualified form refers to an item in the SpaceSystem the reference is used in. It is illegal for a name reference to point to no item (“a dangling name reference”).</documentation>
</annotation>
<restriction base="normalizedString">
<pattern value="/?(([^./:\[\]]|\.|\.\.)/)*([^./:\[\]])+"/>
</restriction>
</simpleType>