Rename initial submission to submissions/starting_kit

# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
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# Author:    Roman Yurchak <rth.yurchak@gmail.com>
# Date:      Wed Dec 23 23:05:07 2020 +0000
#
# On branch fix-starting-kit
# Your branch is up to date with 'origin/fix-starting-kit'.
#
# Changes to be committed:
#	renamed:    submissions/linear_regression_rois/estimator.py -> submissions/starting_kit/estimator.py
#
# Untracked files:
#	brain_age_starting_kit.html
#	events_archived/
#
