XTCE13 — Clarify RepeatEntry's values and what they mean

Firstly because repeat is optional, it seems intuitive that this is the same as repeat=0. And that intuitively means the entry repeats 0 times, which means it appears 1 time in the container entry list. Likewise a repeat=1, means the entry appears 2 times and forth. This to me makes sense but maybe it doesn't.
The syntax right now is broad and would allow all sort of values including negative ones. It's not clear that that would be anything but an error.
Given all that we should say something about this in the annotation at the very least. And since FixedValue is a long we could change it to positive-only or perhaps non-negative. The DiscreteLookup value's type could also be modified (we'd have to make a "PositveOnlyDiscreteLookup" or some such). The last is a DynamicLookup and that would have to be enforced outside the syntax, we could imply it by calling it "PositiveOnlyDynamicLookup" or similar.
Finally add annotation.

Improve Annotation on RepeatEntry Elements

The RepeatEntryType annotations are not useful. Propose to make these more specific.

Existing RepeatType:

<complexType name="RepeatType">
<annotation>
<documentation xml:lang="en">Hold a structure that can be repeated X times, where X is the Count</documentation>
</annotation>
<sequence>
<element name="Count" type="xtce:IntegerValueType">
<annotation>
<documentation xml:lang="en">Value (either fixed or dynamic) that contains the count of repeated structures.</documentation>
</annotation>
</element>
<element name="Offset" type="xtce:IntegerValueType" minOccurs="0"/>
</sequence>
</complexType>

New RepeatType:

<complexType name="RepeatType">
<annotation>
<documentation xml:lang="en">Contains elements that describe how an Entry is identically repeated. This includes a Count of the number of appearances and an optional Offset in bits that may occur between appearances. A Count of 1 indicates no repetition. The Offset default is 0 when not specified.</documentation>
</annotation>
<sequence>
<element name="Count" type="xtce:IntegerValueType">
<annotation>
<documentation xml:lang="en">Value (either fixed or dynamic) that contains the count of appearances for an Entry. The value must be positive where 1 is the same as not specifying a RepeatEntry element at all.</documentation>
</annotation>
</element>
<element name="Offset" type="xtce:IntegerValueType" minOccurs="0">
<annotation>
<documentation xml:lang="en">Value (either fixed or dynamic) that contains an optional offset in bits between repeats of the Entry. The default is 0, which is contiguous. The value must be 0 or positive. Empty offset after the last repeat count is not implicitly reserved, so the parent EntryList should consider if these are occupied bits when placing the next Entry.</documentation>
</annotation>
</element>
</sequence>
</complexType>