Cleanup: 
Introduced ExtendedSuffixArray class.
Moved split_lcp_array_into_intervals method from LCPInterval class to
ExtendedSuffixArray class.
Moved list_prefixes method from LCPInterval class to ExtendedSuffixArray
class.
Removed get_lcp_intervals method from Collation class.
Removed calculate_sub_lcp_intervals method from Collation class.
Removed split_lcp_intervals method from Collation class.
Removed calculate_potential_blocks from Collation class.