Squashed 'cmake-modules/' content from commit 29bed22

git-subtree-dir: cmake-modules
git-subtree-split: 29bed2226f33a6c2987f3e1bd309e6fdb6c8850f
Merge commit 'ce5baef46f9ba6045edb3c9323227b15fc4dc2f4' as 'cmake-modules'
Removed old CMakeModules folder
replaced ADD_MSVC_PRECOMPILED_HEADER with add_pch
added the new cmake-modules folder to the cmake modules path, included AddPch and ConditionalSources at the root level.
temporary measure - moved ADD_MSVC_DISABLED_FILES to root cmake lists file
Updated FindThreads
replaced ADD_MSVC_DISABLED_FILES
Fixed extranious ... which was screwing up ARGV
Started using ARGV instead of ARGN when parsing source files
added helper function to conditional sources for parsing the arguments, made FILES specifier optional.
Fixed handling of multi-part conditional variables
added some usage of the conditional_sources functions, cleaned up existing one
Merge pull request #220 from leapmotion/feature-cmake-modules

Feature cmake modules