Timeout commands

[enlight]

I've run into an issue with lldb-mi on Windows (though my Ubuntu VM fares no better) where attempting to connect to a remote target that is unreachable results in lldb-mi just sitting there forever without responding to anything. Arguably this is a bug in lldb-mi (or maybe lldb itself, or the host-only VirtualBox network driver) but dbgmits should be able to recover from this sort of situation by terminating the lldb-mi process and throwing a suitable error if a response is not received within a reasonable amount of time. The amount of time a command is expected to take may differ from one command to the next, so it should be possible to specify the timeout value per command, however for ease of use there should be a way to specify a default timeout for certain categories of commands.