Add memory efficient version of ErrorAlignment

[kche309]

https://github.com/LinguaPhylo/linguaPhylo/blob/master/lphy-base/src/main/java/lphy/base/evolution/alignment/ErrorAlignment.java

For large alignments, if the fraction of error is small use a memory efficient version of ErrorAlignment (e.g., fraction estimated from a sample of 1000 sites).

Memory efficient version of ErrorAlignment should store i,j indices of sites with errors.