Updating some types from structure-support-2 branch to make sure the code generator works

source/physics/mechanics/real_world_length_unit_info.xml

     <field name="unit" id="0" since-version="0">
         <type name="physics.mechanics.real_world_length_unit"/>
         <description language="en-US">Length measurement unit.</description>
+        <value>meter</value>
     </field>
 
     <description language="en-US">

source/science/value_with_unit.xml

     <field name="value" id="0" since-version="0">
         <type type-argument-name="value_type"/>
         <description language="en-US">Numeric value.</description>
+        <value>primitive=0</value>
     </field>
     <field name="unit" id="1" since-version="0">
         <type type-argument-name="unit_type"/>
         <description language="en-US">Unit the numeric value is measured in.</description>
+        <value>default-unbound-value</value>
     </field>
     <field name="unit_conversion_context" id="2" since-version="0">
-        <type type-argument-name="value_type"/>
+        <type type-argument-name="unit_conversion_context_type"/>
         <description language="en-US">Context that defines how to convert numeric value between units, if required. Contains all required external data: dates for currency exchange rates, DPIs to convert between physical sizes and pixel counts, etc.</description>
+        <value>default-unbound-value</value>
     </field>
 
     <description language="en-US">