Add ability to add or update multiple entries in configuration store

[schandrika]

Is your feature request related to a problem? Please describe.
With automatic agent configuration generation and automated ansible deployment scripts, we are able to setup volttron and configure and install multiple agents all using a automated script that can be repeated for different hosts. However this process is currently slows down considerably when adding configurations to configuration_store. This is because currently we can add only one config entry at a time using "vctl config store" command. This is one round trip per config addition. For VOLTTRON Intellimation TCF project we auto generate driver configs, economizer configs, and ILC agent configs for multiple devices using haystack tags. Generating these tags takes only a few seconds however storing these tags one at time takes hours.

Describe the solution you'd like
Add feature to add/update multiple configuration entries at the same. This could be done

1. When VOLTTRON is not running through vcfg command. This would be useful to for initial automated volttron and agent setup
2. When VOLTTRON is running - Add rpc method to configuration store to send multiple configs, compressed as .tgz file that can be add one at time on the server end.