Migrate logging to use RPC Logging methods

[hanzei]

Instead of using mlog all log calls should use the RPC methods LogX, e.g. LogDebug. This allows the server to gradually select which log messages to show in the server logs.

[mo2menelzeiny]

@hanzei, I'm giving this a shot.
I don't know if this is the right place, but I'm having trouble with the testing.
Does any test cases cover the thrown errors? or do I have to manually test this?

My attempt for example

if err != nil {
        mlog.Error(fmt.Sprintf("Error creating autolinker: %+v: %v", c.Links[i], err))
}

I'm going to replace it with

if err != nil {
	p.API.LogError(fmt.Sprintf("Error creating autolinker: %+v: %v", c.Links[i], err))
}

do I even need to validate?

[hanzei]

@mo2menelzeiny Please see my response in your PR: #102 (comment)