Upgrade Linaro release, FVPs and mbed TLS versions

This patch updates the User Guide to recommend the latest version
of some of the software dependencies of ARM Trusted Firmware.

 - Upgrade Linaro release:     16.02 -> 16.06

 - Upgrade FVPs
    - Foundation v8 FVP:       9.5 -> 10.1
    - Base FVPs:               7.6 -> 7.7

 - Upgrade mbed TLS library:   2.2.0 -> 2.2.1

Note that the latest release of mbed TLS as of today is 2.3.0 but it has
compilations issues with the set of library configuration options that
Trusted Firmware uses. 2.2.1 is the next most recent release known to
build with TF.

This patch also fixes the markdown formatting of a link in the
User Guide.

Change-Id: Ieb7dd336f4d3110fba060afec4ad580ae707a8f1