Prevent Dumping and Loading Checkpoints During Run Mode

[Mrockwell2]

Solves issue #1461 while also allowing for scheduling checkpoints at future times and using trick.add_read to load checkpoints at specific times.

[Mrockwell2]

Just found that this might break Master-Slave. The Slave can mimic the Master automatically when it dumps or loads a checkpoint. Going to have to look at how the Master dumps and loads checkpoints. I'm also going to create an issue that MasterSlave has no tests.

[coveralls]

coverage: 56.241% (+0.4%) from 55.827%
when pulling 50dc60e on Mrockwell2:1461-edit-checkpoint-at-time
into 37e273a on nasa:master.

[coveralls]

coverage: 56.25% (+0.4%) from 55.827%
when pulling 50dc60e on Mrockwell2:1461-edit-checkpoint-at-time
into 37e273a on nasa:master.

[coveralls]

coverage: 56.241% (+0.4%) from 55.827%
when pulling 7821695 on Mrockwell2:1461-edit-checkpoint-at-time
into 37e273a on nasa:master.

[coveralls]

coverage: 56.245% (+0.4%) from 55.827%
when pulling 0926010 on Mrockwell2:1461-edit-checkpoint-at-time
into 37e273a on nasa:master.

[coveralls]

coverage: 56.3% (+0.4%) from 55.891%
when pulling cebc83f on Mrockwell2:1461-edit-checkpoint-at-time
into 92b0168 on nasa:master.