add method for getting number of alphabet bits for multiple files in GammaRLDecoder class
add method for setting bwt file vector and size of vector in BwtMergeBlockSortResult class
make bwt file set a vector instead of a single file in BwtMergeTempFileNameSet
make number of bwt files a parameter in BwtMergeTempFileNameSetVector
fix license header
extend constructWaveletTreeFromRlWithTerm method in Utf8ToImpCompactHuffmanWaveletTree to take a vector of input files instead of a single file