SH-1990 Fix for redundantly applying some color scaling to sky and water (also add some snazzy specular bloom from the sun)

SH-2031 High risk changeset, but potentially high reward.  Addresses frame stalls in renderer by never using the fixed function pipeline if shaders are available.

SH-1682 Dynamically adjust the number of texture channels to use for indexed texture rendering based on available hardware.

SH-469 Don't use depth buffers and multisample buffers where not absolutely needed -- make sample counts consistent between shaders and render targets.

* Fixed ATI mac "lighting and shadows" related crash
* Fixed up numerous GL errors on macs related to multiple color formats,
  the use of glEnable/glDisable on textures above the texture unit count
  and old ATI-specific code that was not appropriate for Mac.
* Disabled SSAO for ATI macs due to it not working with shadows
* Ongoing work to properly get shadows and SSAO functioning on ATI macs is required.

Reviewed by davep

* Disabled SSAO on macs with 8 or less texture units.
* Slight cleanup of sunlight fragment shaders to remove unused texture units.

Reviewed by davep

* Modified mac feature table to bring it up to date with latest renderer features including deferred rendering
* Changed mac AGL pixel format to no longer allow it to revert to software rendering when shader compilation errors occur.
* Fixed up various GLSL shader compilation warnings and errors that came up as a result of the above changes.
* Changed initial conditions for the "hardware skinning" checkbox on the preferences floater so it can be modified before login on machines that support avatar vertex programs.
* Removed unused avatarAlphaF.glsl files

Reviewed by davep

SH-1455 Faster, better, more reliable disabling of DoF effect when edit menu is open and when effect is opted out of.

SH-547 Fix for rigged attachments being invisible in impostors and fix for impostors not working with lighting and shadows enabled.

SH-958 Fix for entire scene being in shadow when shadows + SSAO disabled but "Lighting and Shadows" enabled.

(transplanted from a38a7ea07c52aafbd4305f96d715201a35d86726)

(transplanted from e41d116728dd1e453273047ba7fde9455a1811d4)

(transplanted from 4b7066a9a309fa82727c0b403cc6f20720077dc0)

followup - remove the distance limiting, re-enabling distant SSAO.
(transplanted from d11eafacb2609537905718fa559e81b53e6740f8)

(transplanted from ef938dea0504b12fcf802f38fcf5457ba566c468)

(transplanted from c698ce37c0502597aafc75fcf9c37ff2970b7faf)
(transplanted from ae92e806703a0c03ec2ab76d74906c7465285aaf)