Telemetry scheduler

Allow periods to be set to zero since it is easier than changing the updatemode.
Allow hiding of objects not present on hw.
Only apply and save metaobjects which were actually changed.
Several misc fixes. 
If I'm reading this correctly, all the code below only matters when this block is NOT executed. Why not move it all into the above if statement? 

When this is set to -1 the object is not appended and thus the update doesn't happen, right?