[TC-501] TPv2 installation - better defaults are required

[limited]

After basic install of traffic-portal based on the documentation, traffic portal failed to launch. this is due to relative pathes to the logs and static files appear in the default configuration.
Note that the working directory of the server is "/"

First, the log path (./server/log) does not exists. A possible fix is to change the dir to /opt/traffic_portal/server/log and create the log dir if needed.

Second. the files static path should be set to "opt/traffic_portal/public"

Author: Nir Sopher
JIRA Link: https://issues.apache.org/jira/browse/TC-501
Found Version: 2.1.0

[mitchell852]

Following the comments found in config.js will correct this problem.

https://github.com/apache/incubator-trafficcontrol/blob/master/traffic_portal/conf/config.js