Having all indentation made browsing the generated doxygen source code
unbearable.

Also updated the install path for the cmake files so it doesn't pollute
the install prefix.

	modified:   cmake/DD4hepMacros.cmake
	modified:   doc/doxygen/DD4hep.css
	modified:   doc/doxygen/DD4hepFooter.html
	modified:   doc/doxygen/DD4hepHeader.html

 - also set DD4HEP_LIBRARYPATH in dd4hep_add_library_path()
 - export ROOTSYS if it has not been set
    ( assumes path_to_ROOT/cmake )

Remove minimum required cmake version from DD4hepBuild, this interferes with other packages depending on DD4hep

whitepsace

also remove where visited the $ statements in the files. They are useless, since git does not support them.
Fixed some tests, which no longer properly worked in the conditions area.

- Attempt to fix MacOSX builds

  - Improve conditions handling. Started to implement using simple telescope
    detector from C.Burr.
  - Add variable DD4HEP_LIBRARY_PATH to be used on MacOSX El Capitane
    to overcome DYLD_LIBRARY_PATH protection issues.
  - Fix to copy with negative(rebased) IDDDescriptor fields
    (affects IDDDescriptor and VolumeManager).
    2 New tests:
    - ClientTests/Bitfield_SidesTest.xml to test readout string:
      system:8,barrel:-2
    - ClientTests/Bitfield_SidesTest2.xml to test readout string:
      system:16,barrel:16:-5