* Fix context.cloth, was not being set correct.
* Fix errors with context pinning, scripts should
not assume context.object to be there.
* Always show preview even if e.g. the material is not
set, to keep ID buttons from jumping while you're
using them.
* Close some material/texture panels by default.
* Update material buttons to use more diffuse/specular variables.
* Don't show texture mapping/influence when the texture is pinned.
* Small visual tweak for sequencer header menus.
* 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.
