Refactor: Convert install/uninstall script to just source the rc file

This was much cleaner than trying to determine what all the variables were that
needed to be set up to make the scripts run.

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Change-Id:     Ib8ab869437626adc123ae62c521dc52215ed1ca9
Signed-off-by: Jeff Felchner <accounts+git@thekompanee.com>
Refactor: Fix check for existence of SW_PLUGINS

For some reason Bash doesn't do the shortcut very well so we have to do it the
long way.

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Change-Id:     I786be7480fa1fcaa0f859f9b5380e26a690d7724
Signed-off-by: Jeff Felchner <accounts+git@thekompanee.com>