install gems at `vendor/bundle`
removed the DB_INIT script variable.
specify absolute path to the VERSION file
create VERSION file as redmine user
create tmp directory in data volume
moved VERSION file to ${DATA_DIR}/tmp/
moved gem bundle to ${DATA_DIR}/tmp/ at migration

For user plugin installation it is absolutely necessary that
the gems are located in the data volume because some plugins
require gems to be installed.

Moving the gems bundle to the data volume will make sure that the gems
installed by plugins are available when the container is restarted.

Whenever there is a version update, the bundle directory will be removed
and the plugins gems would need to be reinstalled.
moved `tmp/thumbnails` to data volume
moved secret_token file to ${DATA_DIR}/tmp/ for persistence

With this change user sessions token will remain valid even if the
container is stopped and started again since the secure token will not
change.
Generate the secure token only on version updates.
removed pre-install plugins
removed app:db:migrate command

The database migration is automatically done. If the user wishes to
manually run the database migrations, they can execute the rake task
using `app:rake db:migrate` command
merge appDbMigrate into appStart function
added system for users to install plugins in the `${DATA_DIR}/plugins/` directory
moved Gemfile.lock to ${DATA_DIR}/tmp/
move `public/plugin_assets` to ${DATA_DIR}/tmp/

plugins install assets in the `public/plugin_assets` directory. This
directory has to persistent to avoid running the plugin migrations at
every startup everytime.
fix ownership of `${DATA_DIR}/tmp/` before starting the application
do not silence migrations
touch `log/production.log` at install
removed pre-installed themes