Consider adding a fullLogName(String) to LoggingOptions

[mziccard]

We could add a LoggingOptions.fullLogName(String) method that given a log name like "syslog" returns the fully qualified name "projects//logs/syslog".

This method is of no use in our service calls as our params must be partial names but could be useful to users when building filters like: "logName=projects//logs/syslog".

[danoscarmike]

This has been added to our feature backlog: https://github.com/GoogleCloudPlatform/google-cloud-java/wiki/Feature-backlog. This issue will be closed but is linked in the backlog and can continue to be used for comment and discussion.