Chunk feature access

[EmmanuelP]

chunkparser: allow to set string and integer features

On some devices, chunk access requires a change of a local feature value. For
example:

 <Enumeration NameSpace="Standard" Name="ChunkComponentSelector">
  <Visibility>Expert</Visibility>
  <EnumEntry NameSpace="Standard" Name="Range">
   <Value>0</Value>
  </EnumEntry>
  <EnumEntry NameSpace="Standard" Name="Normal">
   <Value>1</Value>
  </EnumEntry>
  <EnumEntry NameSpace="Standard" Name="Texture">
   <Value>2</Value>
  </EnumEntry>
  <Value>0</Value>
 </Enumeration>

  <Float NameSpace="Standard" Name="ChunkScan3dCoordinateOffset">
  <Visibility>Expert</Visibility>
  <ImposedAccessMode>RO</ImposedAccessMode>
  <pValue>ChunkScan3dCoordinateOffsetRegister</pValue>
  <Min>-3.40282e+38</Min>
  <Max>3.40282e+38</Max>
  <Inc>1e-6</Inc>
  <DisplayPrecision>6</DisplayPrecision>
 </Float>

 <FloatReg NameSpace="Custom" Name="ChunkScan3dCoordinateOffsetRegister">
  <Visibility>Expert</Visibility>
  <Address>0x8</Address>
  <pIndex Offset="16">ChunkComponentSelector</pIndex>
  <Length>8</Length>
  <AccessMode>RW</AccessMode>
  <pPort>Chunk</pPort>
  <pInvalidator>ChunkScan3dCoordinateSelector</pInvalidator>
  <pInvalidator>ChunkComponentSelector</pInvalidator>
  <Endianess>LittleEndian</Endianess>
 </FloatReg>

As the Genicam tree is owned by the parser and not shared with the device, in
order to access to chunk data without a device instance, we need to provide an
API to set the selector feature.

arv_chunk_parser_set_string_feature_value (parser,
					   "ChunkComponentSelector",
					   "Normal", &error);
normal_offset = arv_chunk_parser_get_float_value (parser,
						  "ChunkScan3dCoordinateOffset",
						  &error);