Function naming and API

[adknudson]

In an effort to achieve a 1.0 stable release, consider the following functions that can be merged by a unifying api or function:

• cor_convert, pearson_match
• cor_bounds, pearson_bounds
• rvec
• cor, cor_fast
• cor_nearPD, cor_fastPD
• cor_randPD, cor_randPSD

These functions can be merged and changed to be non-exported functions

• cor_constrain, cov2cor, clamp, cor_clamp

[adknudson]

while some of the functions could be merged, I am choosing to leave the current API as is. Nearest correlation matrix methods have been broken off into its own package (NearestCorrelationMatrix) which has a unified API, so the cor_nearPD methods can be left as is for convenience.

cov2cor doesn't need to be exported, but R users may find it useful, so it will stay.