Start of CZML clock work.
Merge branch 'master' into czmlClock
Merge branch 'master' into czmlClock
Add DynamicClock object and specs.

I'm not thrilled, but it gets the job done.
Add doc and fix a few typos.
Merge branch 'master' into czmlClock
Fix race condition in ClockViewmode.synchonize.

Setting values in the view model would cause other values in the clock to change.  Since we want to synchonize the viewModel with all clock settings, we need to copy the current clock settings to temporary variables, and then set from there.
Merge pull request #598 from AnalyticalGraphicsInc/czmlClock

Support for CZML defined clocks.