Increase voice conf length

 We need to increase the length of the voice conference. If we have lots of meetings running,
 there is a high chance of collision.

 Need corresponding changes to FreeSWITCH dialplan.

 In bbb_echo_test.xml, change to `expression="^echo(\d{5,11})$"`.

 In bbb_conference.xml, change to `expression="^(\d{5,11})$"`.