option output according to time interval (not timestep interval)

[mooseframework]

It would be very useful to have the option to output according to fixed time intervals rather than time step intervals. This would be an extension of the sync_times option in which output would only be written at specified simulation time intervals.

[mooseframework]

In 401b63f:

Added ability to specify the interval in time at which to output, it is simliar to sync times but is specified by a single time interval (Real) and only outputs at those time intervals (and any other specified sync times), created boolean for keepgoing() as return variable. Made it so that if steady state, number of timesteps, or time returns false that the output is printed if the output interval did not already print out output, output is not done only in case of abort on solve fail, as the solve failed. ref #1781 and ref #1772

[mooseframework]

There is some chance that in the case of the interval in time it might output the final solve twice if the final solve is a synctime. I am thinking of setting a bool in feproblem which gets set to false at the start of every timestep, true if output occurs, and is checked in transient in keepgoing() if keepgoinng will return false.

[mooseframework]

In c6b2308:

ref #1772 ref #1781 possibly ref #1599 if I knew for sure what is being referred to there. Created a test for the time intervals, changed it to the output block, made it so that the end time doesn't need to be set at all. Changed  sync_times to be a set instead of vector, changed the tollerances in sync_times so that a time step that is below _dtmin is not taken, instead if it is within _dtmin of the sync time (or time interval) then it is assumed to have hit the time requested, this prevents solve failures and crashes when the solve fails and the time step size is below _dtmin. Created test for the output of the last time period and for the time intervals (it is the same test, with the time period set so that the final step will not have output previously. Made it so that if the final step does land on a sync time it doesn't output twice, added an output bool set to false in transient at the start of a time step and true if output occurs during the time step. Interval works with time_interval now. I think that might be it.

[mooseframework]

In 020ce3f:

ref #1772 ref #1781 actually adds the tests

[aeslaughter]

move to #3487