Install examples to doc dir and lib (#82)

Install most of the example files to the doc folder, except on
UNIX, when the executable examples go to a subfolder of lib
with a symbolic link installed to the doc folder.
Clarify test/example cmake settings.

This commit attempts to fix issue #92 via the following changes:

* Rename BUILD_TESTING_{STATIC,SHARED} to
  BUILD_TESTS_AND_EXAMPLES_{STATIC,SHARED}, everywhere.
* In the comments for BUILD_TESTING and BUILD_EXAMPLES, mention the
  importance of BUILD_TESTS_AND_EXAMPLES_{STATIC,SHARED}.
* Edit comment for BUILD_TESTS_AND_EXAMPLES{STATIC,SHARED}.
* Add CMake errors if the user wants tests or examples but sets both
  BUILD_TESTS_AND_EXAMPLES_{STATIC,SHARED} off.
Merge pull request #95 from chrisdembia/issue92

Clarify test/example cmake settings.
Provide access to normalizeQuaternions() method, previously internal only.
Merge branch 'issue_82' of https://github.com/scpeters/simbody into scpeters-issue_82

Conflicts:
	Simbody/examples/CMakeLists.txt