doc: add a troubleshooting guide

In preparation for more strict guidelines on documentation, provide a
trouble shooting guide with the most common and obscure issues found.

The CI system will point to this guide to help committers upon doc
failures.

Change-Id: I386baea75dad0c82b58b23926e0bd32de8a0b249
Signed-off-by: Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>