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

[facebook-github-bot]

Thank you for your pull request and welcome to our community. We require contributors to sign our Contributor License Agreement, and we don't seem to have you on file. In order for us to review and merge your code, please sign up at https://code.facebook.com/cla. If you are contributing on behalf of someone else (eg your employer), the individual CLA may not be sufficient and your employer may need the corporate CLA signed.

If you have received this in error or have any questions, please contact us at [email protected]. Thanks!

[facebook-github-bot]

Thank you for signing our Contributor License Agreement. We can now accept your code for this (and any) Facebook open source project. Thanks!

[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.