PAM-A dycore work

- (Done) Reduce total kernel count in spatial operator
* (Done)This will mainly involve pulling BC kernels into other kernels
* (Done) Go ahead and assume periodic BCs in horizontal and solid wall in vertical for simplicity

## RK
- Separate ADER from RK spatial operators
- Update RK to work with new interface requirements
- Update RK to do splitting trivially within each stage

## Vertical Acoustic Subcycling
- Maybe start with multi level parallelism with the full vertical solver as a beginning stopgap. No critical decisions or new algorithmic development necessary. Just new functionality in YAKL.
- Determine which terms need vertical momentum to be *acoustically* upwind and which terms can have it ben advectively upwind
- Create RK and ADER options that subcycle vertical dynamics as a whole
- Create a sub-cycled version of rho, rho*w, and rho*theta
* Mass consistent, stable upwinding
* ADER will take some figuring out to compute rho*w DTs over larger advective time step
* RK will take figuring out as well, I think