* Added more material buttons by William. Thanks.
I made some minor adjustments and added Specular Shader Model RNA.
* Code cleanup and some consistency tweaks of button files.
Notes: Preview render now only shows up when there is an active world, material, texture or lamp.
* Made sure initial panels with ID Datablocks are shown, even when no block is active.
* Context now allows pinning a datablock, independent of
selection.
* Initial ID browse buttons for most buttons tabs.
* Browsing from world to texture now displays world textures
again, but is a bit of a hack, not sure there is a right
way to do this.
* There's a button to switch between active materials and
textures now, only temporary though.
* There's some code to put context part in own region,
disabled still because it doesn't work that well yet.
* Added panels with dummy preview template.
* Added constraints panel for bones next to objects, though it
doesn't work that well yet, the operators and code need to be
changed so they don't assume it is one or the other in/out
of posemode.
* Added some graying out in the scene and world buttons.
note: The new 'Toggle' options in the UI api should be
avoided for normal text buttons, and used sparingly
otherwise. We want to avoid having two inconsistent
appearances for the same type of buttons.
* Buttons are now created first, and after that the layout is computed.
This means the layout engine now works at button level, and makes it
easier to write templates. Otherwise you had to store all info and
create the buttons later.
* Added interface_templates.c as a separate file to put templates in.
These can contain regular buttons, and can be put in a Free layout,
which means you can specify manual coordinates, but still get nested
correct inside other layouts.
* API was changed to allow better nesting. Previously items were added
in the last added layout specifier, i.e. one level up in the layout
hierarchy. This doesn't work well in always, so now when creating things
like rows or columns it always returns a layout which you have to add
the items in. All py scripts were updated to follow this.
* Computing the layout now goes in two passes, first estimating the
required width/height of all nested layouts, and then in the second
pass using the results of that to decide on the actual locations.
* Enum and array buttons now follow the direction of the layout, i.e.
they are vertical or horizontal depending if they are in a column or row.
* Color properties now get a color picker, and only get the additional
RGB sliders with Expand=True.
* File/directory string properties now get a button next to them for
opening the file browse, though this is not implemented yet.
* Layout items can now be aligned, set align=True when creating a column,
row, etc.
* Buttons now get a minimum width of one icon (avoids squashing icon
buttons).
* Moved some more space variables into Style.
* Made separator item work horizontal & vertical.
* Add colon (:) automatic for int/float/enum/string.
* Added space variables to uiStyle and use them in the
layout engine.
* Added initial World buttons by Thomas Dinges, thanks!
* Added some code for modifiers in the Object Data context.
This will become a template though.
* Use a common poll() callback in the scripts to reduce code.
