Log master ui bugfix for when nodes have zero log entries
Implemented some central control over logging settings
node_log_client is a component, has debugging UI and automatic limiting of memory usage

renamed log_client to node_log_client.

node_log_client is now a normal component. It has a UI screen where the latest N lines of log contents can be inspected. If node_log_client is unable to talk to the node_log_master for a long time, only the M latest lines of log get sent over. N and M are configurable from the config_master.