Add Support for JuiceSSH

This PR adds support for JuiceSSH as requested in #141.

This might not be the most elegant way, seeing that we're adding another icon and settings-holder for JuiceSSH next to IrssiConnectbot - when even more clients are added, this probably won't be scaling very well...

But for the meantime, where we just have 2 clients, this should do just fine :-)

Unfortunately, JuiceSSH does not offer a way as easy as IrssiConnectbot does for retrieving and using connections - we have to use their plugin-system - this also means, we have two new permissions on board (com.sonelli.juicessh.api.v1.permission.READ_CONNECTIONS and com.sonelli.juicessh.api.v1.permission.OPEN_SESSIONS). But as they are non-vital to the functioning of the app, they will only be requested during runtime when JuiceSSH is installed on the device and the user requests to link his device to JuiceSSH.

该提问来源于开源项目：murgo/IrssiNotifier