Load
====
Photoshop 2.0 and lower files are not supported due to lack of 
file specs and test files.

Add text names for colour modes

Parasite for layer blending ranges per channel?

Read & use global mask data

Check for block over-run in read_channel_data

Process errors from readers in read_channel_data

Invert layer mask - channel_set_show_masked or invert mask + parasite

decode more image resources

Read in layer resources and process adjustment layers etc.
add parasites as required - should be similar to image resources

add layer support for:

Text layers

vector masks

Image resources:
================

1005 - resolution
  width and height units dropped.

1007 - Display info
  save colour space & colour as parasite if unable to display.

1008 - caption - Add to XMP data block.

1025 - Working path (not saved) - Load

1026 - Layers Group Info - ?Load

1033 1036
  Better error handling for Jpeg decompression. Check for JPEG being included
  Custom error function.

1041 - Honour ICC untagged option

2000-2998 - Paths
  Add initial fill rule and clipboard parasites.

2999 - Clipping path
  Add as parasite to path record.
