Remove unused arguments and imports

[Proyag]

• Removed unused lower_case argument in Token and TokenLine
• Removed unused (and confusing) line argument in BPEfastLoad
• Removed unused imports in mine_bitexts.py
• Removed MOSES_LC in text_processing.py which pointed to the no longer used Moses lowercasing script

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[hoschwenk]

Thanks a lot for cleaning up the code !
I would prefer to keep the lower_case flag even though it is currently not used.
Future version of LASER may be case sensitive :-)

[Proyag]

Fair enough. Reverted those changes.