assword: Added possibility to nicely handle password epiration from other plugins (#5468)

Squashed commit of the following:

commit 41283ecab18321201c3adfef8e964e2aa0dc2032
Author: Aleksander Machniak <alec@alec.pl>
Date: Sat Oct 15 08:37:31 2016 +0200

CS fixes after PR merge, renamed session variable

commit b4440a0c4d15c194619c003683ff0d36787f82a8
Merge: cf9f0d8 5dee181
Author: Aleksander Machniak <alec@alec.pl>
Date: Sat Oct 15 08:26:04 2016 +0200

Merge branch 'master' of https://github.com/ZiBiS/roundcubemail into ZiBiS-master

commit 5dee1812e7cb65037429b8cf7fa26744cc2ba5d0
Author: Zbigniew Szmyd <zbigniew.szmyd@linseco.pl>
Date: Thu Oct 13 14:20:14 2016 +0200

passing by session

commit 6ccb7e7d1d7293b7b6448aef41f1f8fead71bda4
Author: Zbigniew Szmyd <zbigniew.szmyd@linseco.pl>
Date: Thu Oct 13 11:45:43 2016 +0200

formatted passwdexpdatetime should be set in session data

commit a43f30fdfc599db235d78137eee9e1f0dd2412b7
Author: Zbigniew Szmyd <zbigniew.szmyd@linseco.pl>
Date: Thu Oct 13 11:10:06 2016 +0200

_passwdexpwarning removed and expdatetime object is stored in session

commit 62ef852a112944b3a222ccdb4aa87510e5de4b09
Author: Zbigniew Szmyd <zbigniew.szmyd@linseco.pl>
Date: Thu Oct 13 10:24:39 2016 +0200

String concatenation is removed and expdatetime is passed via session
data.

commit 2aea3a4e85b751bdf329eaaa69a8bee09d70cd49
Author: Zbigniew Szmyd <zbigniew.szmyd@linseco.pl>
Date: Wed Oct 12 10:20:58 2016 +0200

Removing ppolicy plugin from my repository.

commit 8848c944ab8e699c13f81abfb0e64a20b27bc9eb
Author: Zbigniew Szmyd <zbigniew.szmyd@linseco.pl>
Date: Tue Oct 11 11:32:37 2016 +0200

little correction of variables names

commit 5266c89da9bce20286dca7c6c1a6be8121481902
Author: Zbigniew Szmyd <zbigniew.szmyd@linseco.pl>
Date: Tue Oct 11 11:14:17 2016 +0200

little corrections

commit c665b5c6075e843d6f935fc88cbfbd368be8037a
Author: Zbigniew Szmyd <zbigniew.szmyd@linseco.pl>
Date: Tue Oct 11 10:31:05 2016 +0200

A plugin to check LDAP password for expiration