Logging support in rbus with Tags

[goutham24693]

Add a log file for rbus transaction in /rdklogs/logs directory. eg: /rdklogs/logs/RBUS.txt.0

Every component that registers with r-bus should have a TAG.
A group of component can have same TAG.

for eg: wanmanager, dslagaent, ethagent, pppmanager, dhcpmanager can have tag - WAN

and all the GET/SET/Publish should be logged in to /rdklogs/logs/RBUS.txt.0 along with the tag.

when developer does,

`$ cat /rdklogs/logs/RBUS.txt.0       # dev should see all bus tx in the device (Local & Remote)`

`$ cat /rdklogs/logs/RBUS.txt.0 | grep "<TAG-NAME>"          # dev should be all rbus tx within the tag`

#eg: 
$ cat /rdklogs/logs/RBUS.txt.0 | grep "WAN"       # dev can see communication between all wan components.

Tags are similar to log level (INFO, DEBUG, etc ) except they are used to group components.
adding common tags between related component can help debug better in areas such as wan, wifi, gatewaymgr, lan

Log file should be included in log rotation and backing up mechanism.
Log file can be very helpful in triaging/debugging customer issues & to narrow down which component has issue instead of looking at separate component specific files.