Replace custom support of bcrypt and sha1 by passlib

We could probably safe some lines of code by re-using passlib.
Fo bcrypt, the migration should not be to difficult and neither for sha1 (aka sha1_crypt)

https://pypi.python.org/pypi/passlib

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assigned to @ced

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Here is review51461002 which keep the old methods but update the hash on the first login. This should progressively migrate the password hashes and allow to remove the code on the next major release.
I still have to update web_user with the same design if we agree on this one.

review51461002 updated at https://codereview.tryton.org/51461002/#ps1

review51461002 updated at https://codereview.tryton.org/51461002/#ps20001

review51461002 updated at https://codereview.tryton.org/51461002/#ps40001

review51461002 updated at https://codereview.tryton.org/51461002/#ps60001

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New changeset 182ba1d53b16 by Cédric Krier in branch 'default':
Use passlib
https://hg.tryton.org/modules/web_user/rev/182ba1d53b16

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closed

New changeset cc5aba3b12c7 by Cédric Krier in branch 'default':
Use passlib
https://hg.tryton.org/trytond/rev/cc5aba3b12c7

New changeset bbe233019d27 by Cédric Krier in branch 'default':
Use passlib
https://hg.tryton.org/tryton-env/rev/bbe233019d27

mentioned in issue #12936 (closed)