Add note about new flavor ID validation

https://review.openstack.org/39441 introduce new
validation code for the flavor ID.

This patch adds a note to ensure people are using correct
numbers when manipulating flavor ids.

Change-Id: Iabecb974beb96da6e8610e097633ad9699655d3e
Closes-Bug: 1217238
Merge "Add note about new flavor ID validation"
adding training-guide card006 content

virtualbox configuration content added to the training-guides

implements bp/training-manuals

Change-Id: I14a7d159d3a856d8e62c7f6a3d4b1c9c490b3712