CompoundPlugValueWidget remembers collapse state.

State is stored on a hidden, non-serialisable plug on the node, and updated whenever the collapse status changes. On building a new ui, we restore any previously stored state.
Node Editor remembers current tab.

Node Editor stores the last viewed tab on a non-serialisable plug on the node, and uses it to set the current tab when generating new uis.

Fixes #87.
Improved NodeEditor node labelling.

The node name field is clearly labelled as such, and an additional info icon provides the node type and description.
fixed a bug in the NodeGraph where setTitle() was having no effect
Merge branch 'master' of https://github.com/ImageEngine/gaffer
Added and empty LINKFLAGS option to SConstruct.
Without it, SCons won't respect if LINKFLAGS is specified in a config file.
Merge pull request #216 from johnhaddon/linkFlags

Added an empty LINKFLAGS option to SConstruct.
Merge pull request #196 from johnhaddon/uiCollapseState

Remembering UI state
Merge pull request #215 from johnhaddon/nodeEditorNodeLabel

Improved NodeEditor node labelling.
Updated Changes and bumped minor version.