add basic xtrabackup support to sandbox datasource api

- tarballs are now extracted with the ignore_zeros option and
  if xtrabackup data is detected, a best effort is made to
  run innodbackupex --apply-log
cleanup logging configuration

- use correct name for excluding sarge logging, which is otherwise
  quite verbose in debug mode
- simply dbsake logging config by going back to using basicConfig
upgrade sarge to 0.1.3
make innobackupex invocation prettier

- run relative to datadir so command can be simplified and
  the same command passed to sarge can be logged.  This simplifies
  to innobackupex --apply-logs . > innobackupex.log.  The datadir
  is passed to sarge.run's cwd option to change the working
  directory.
ensure progress bar only terminates once

- the progress bar was detecting a zero-byte read and outputting
  a newline, but in some cases a reader may read multiple zero
  bytes before terminating.  Now a sentinel is triggers when
  the progress bar has hit 100% and only a single newline is
  emitted.
enable progressbar logic when unpacking data tarballs

- This is used if stderr is a tty and when the --data option
  is used to seed the sandbox with some backup data.
consolidate bootstrap logic in templates/bootstrap.sql

- this template is fed values by common.mysql_install_db()
cleanup bootstrap logic

- standard mysql bootstrap scripts are fed into the dbsake
  sandbox bootstrap.sql template
- if the user table is provided externally, disable normal
  bootstrapping logic (i.e. mysql_system_tables_data.sql)
  to avoid errors in the bootstrapping process.
- if the user table is provided externally then generate our own
  REPLACE INTO user statement to ensure a usable root@localhost
  user.  This is done by introspecting the user.frm via the
  dbsake frm api.
remove deprecated bootstrap templates

- bootstrap_initialization and secure_mysql_installation have
  been consolidated in a single bootstrap.sql script now.
Merge branch 'feature/templated_bootstrap' into develop