Get server.name from a file

[xtreding]

In case when server.name isn't specified in EventNative config, we should read it from a file (from app/res folder) and if the file doesn't exist -> create a new one with the generated server name. Let's give this filename - "server.name"

[dimonl]

@xtreding @vklimontovich Hello, can I do it issue for your repo? If you assign it to me, I would very pleasure. Thanks.