Add WDK libraries to MultiAxis device

Add the WDK libraries if they are found as a dependency of MultiAxis
Device.

Also correct misspelling of BUILD_DEVICE_MULTIAXIS that was precenting
some examples from being built.
Mention all variables used in surgsim_add_unit_tests

Readd mention of UNIT_TEST_SHARED_LIBS, UNIT_TEST_SHARED_RELEASE_LIBS,
and UNIT_TEST_SHARED_DEBUG_LIBS in the comment of
surgsim_add_unit_tests. This was lost in the merging of the unit test
macros into one macro.