Added ability to specify custom naming function
Added ability to specify custom naming function

Can now specify custom naming function as fourth argument to
motionCorrect. namingFunction is a handle to a function for naming. If
empty, uses default naming function which is a local function of
motionCorrect. All naming functions must take in the following arguments
(in  order): obj.acqName, nSlice, nChannel, movNum.

HarveyLab/Acquisition2P_class,HarveyLab/Acquisition2P_class