Cmake simplification and various other minor changes

This pull request represents a rework of our build system. In order to support more platforms and fix issues related to the build system (#1201, #1160, #1138, #1072, #970, #847, #720, #459, #345 and #209) this step was necessary. Unfortunately, it included some breaking changes.

Features:
  - Worked on documentation. Preview: http://sithhell.github.io/docs/html/
  - Multiconfiguration builds (i.e. changing the build type in VS directly) should now be supported
  - Removed all "clever" link/compile options to make HPX compatible to other compiled libraries. Flags 
    can easily be changed by setting the CMAKE_CXX_FLAGS option and friends.
  - Removed almost all platform specific checks (modulo some sanity checks and checks to make HPX 
    built out of the box on linux and windows). Platform specific stuff should now belong into toolchain files.
  - Some renaming of HPX cmake variables: http://sithhell.github.io/docs/html/hpx/manual/build_system/building_hpx/cmake_variables.html
  - Support for static linking
  - Removing of unnecessary compile/link flags for external projects
  - Reworked HPX external cmake support to conform to latest CMake state of the art practice: http://www.cmake.org/cmake/help/git-master/manual/cmake-packages.7.html#creating-packages
  - HPX_NO_INSTALL is no longer necessary
  - Moved non "plugin-able" libraries directly to lib/ instead of lib/hpx

In addition some minor fixes to the source code has been done to fix minor issues.