Function renaming and deprecation from #517

[garborg]

This covers more of what was proposed in #517:

• Stop exporting functions already exposed by the included using DataArrays, StatsBase
• Stop exporting read_rda helpers
• Remove functions that had been copied to deprecated.jl from original files
• Move more deprecated functions to deprecated.jl
• More of the proposed deprecations
• More of the proposed renaming

There still isn't great symmetry in the IO function names, but nothing came to mind:

save(filename, df)	loaddf(filename)
writetable(filename, df)	readtable(filename)

[johnmyleswhite]

Great job. This all looks good to me. Have we now removed all internal uses of vecbind*?

[garborg]

Yeah, they were already removed.