beta: select #dimensions for ordination of dissimilarity

biodivMapR v1.9.0

Changes

• Added dimMDS defining number of dimensions to run PCoA for beta diversity
• exported functions from beta library
• updated documentation

Fixes

• corrected weighted distance from nearest neighbors: assign exact coordinates of a sample when dissimilarity = 0
• temporary: discarded evenness from functional diversity as it uses emstreeR and requires binding to mlpack