create tool_setting and tool_link models

fixes PLAT-600

test-plan:
specs pass

Change-Id: Ic7168bb5cca194b16b3c7f92ea51584ba9e747e7
Reviewed-on: https://gerrit.instructure.com/39714
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Brad Humphrey <brad@instructure.com>
Product-Review: Nathan Mills <nathanm@instructure.com>
QA-Review: Nathan Mills <nathanm@instructure.com>