KeePass integration

[pyhedgehog]

MR-712, MR-490, MR-497

Add the possibility to link KeePass entries to mRemoteNG and connect the entries to different servers.

It eases up the administration when changing passwords in a multi-domain environment and adds some extra security.

There are two possible ways to implement:

1. Use protocol of KeePassHttp plugin. (more secure)
2. Add popup window to use auto-type feature of KeePass. (easier to implement)

Both solutions allows using keepass on per-connection basis - something like "Use KeePass" checkbox in connection settings.