XD-953: options metadata

This is a first POC for XD-953.

Supports the following grammar at the NamespaceHandler level atm:
```xml
<xd:options>
   <xd:option name="foo" description="the foo stuff" type="java.lang.Integer" (1)
          default-value="4"    (2)
          default-expression="bar + 5"   (3)
    />
</xd:options>
```

Everything but name is optional
(1) friendly name mappings is in the works (like int for java.lang.Integer)
(2) and (3) are exclusive

There is also code for profile activation, but no NamespaceHandler support yet. Would be:
```xml
<xd:options>
   <xd:profile name="profile1" when="some spel" />
</xd:options>
```