Refactor deploy_plugins() in deploy_plugins.py

[arm4b]

This is an unfinished refactoring sub-task coming from the Add Pylint as a python static code analyzer #298.

The deploy_plugins() function in deploy_plugins.py is failing pylint check on:

scripts/plugins/deploy_plugins.py:24:0: R0914: Too many local variables (36/15) (too-many-locals)
scripts/plugins/deploy_plugins.py:24:0: R0912: Too many branches (19/12) (too-many-branches)
scripts/plugins/deploy_plugins.py:24:0: R0915: Too many statements (104/50) (too-many-statements)

The function has more than 250+ lines and pylint with multiple warnings is a great indicator that it needs to be restructured and divided into smaller logical pieces. For instance:

• Extract it into a new Plugin class perhaps with another layer PluginDeployer (note: PluginInstaller Refactor install_plugins() in install_plugins.py #329 ) with multiple methods, so the interface would be Plugin.deploy() that we can call while iterating over each plugin in the sequence.
• Then another class PluginConfig would handle plugin config parsing and processing.

The check is silenced for now, don't forget to unsilence it when the refactoring is done.