2.5 - Reworked the icon system a bit

2.5 - Reworked the icon system a bit

* After several hours of manual dragging and typing the icon file is now
enlarged and completely reorganised logically, rather than scattered
throughout. This should provide a lot more room for growth, and is  a
lot easier to work with (also allowing more space for toggle buttons
that require two icon slots next to each other). The icon grid has now
25 x 24 icons - hopefully this might last us for a couple more years :)

Some of the naming of icon defines is a bit ancient and can be cleaned
up a bit further. Other devs, if when bringing spaces back, it's
finding the wrong icon, or missing a define, try and look to see if
it's already existing in the new icon file, or drop me a note and I'll
fix it up.

Note: after these changes, older custom blender 2.4 icon
files won't work and will need to be updated to the new layout.

* Enlarged the icons themselves from 15x16 pixels to 16x16 pixels (icon
designer request). This is a more standard size, and is easier to fit
stuff in proportionally.

* Added a bunch more of jendrzych's icons that weren't added previously
since there wasn't space in the icon file (including a few more
modifier icons)

* Tweaked the outliner somewhat, so that instead of just showing a
generic 'object' icon for all objects, it shows 'object type' icons,
per object type. This makes the outliner a lot more useful for browsing
at a glance - a huge row of identical 'object' icons doesn't really
give much useful information. See here:

http://mke3.net/blender/devel/2.5/outliner_obtypes.png