Add external links

Note: Blender add-on is not part of the 'Tools' folder, but I think it fits well in the Tools section.
Merge remote-tracking branch 'remotes/mike3d/patch-4'
Added ParticleEditor2D to Related Projects. Removed BlenderExporter section from Tools page, instead mention it in AssetImporter's section as an alternative.
For Travis CI - only add the test case when the subsystem is enabled.
On non-MSVC compiler, default to 64-bit when host compiler is.
The default can be overriden using URHO3D_64BIT build option as before.
For Travis CI - fix the condition as the env var may not be defined.
Require always registering remote events for reception. Implement a fixed blacklist of remote events that can not be registered (see Network.cpp). Removed obsolete E_WINDOWMESSAGE event definition.
Travis CI: API documentation update at 2014-09-29 11:45:03 UTC.
[ci package]
Prefer the installed DirectX SDK path to avoid link error with VS2010 (64bit).
Fix CMake error in case PREDEFINED_MACROS string is empty.
Allow to prevent modal window's auto dismissing with ESC by calling Window::SetAutoDismiss(false). Purposefully not an attribute to avoid locking up the editor. Closes #471.
Travis CI: API documentation update at 2014-09-29 20:18:04 UTC.
[ci package]
Simplify the construct for guarding against empty output string.
Fix outdated comment.
Merge pull request #1 from urho3d/master

Update