LZ5 v1.4

Changes:

• improved: levels from 13 to 15 (maximum compression ratio)
• added a new parser: LZ5HC_optimal_price_bt
• updated documentation: lz5_Block_format.md and lz5_Frame_format.md
• changed lz5.exe: the "-B" option with block size [1-7] = 64KB, 256KB, 1MB, 4MB, 16MB, 64MB, 256MB (default : 4 = 4MB)