Add usage statements to data functions

[gmuldoon]

• [x] get1DkStats.m
• [x] get1Dk.m
• [x] get2Dk.m
• [x] plot1DkObs.m
• [x] get2DtrueBath.m
• [x] plot2DBath.m
• [x] getBC.m
• [x] get_hOct1.m
• [x] interp_h.m