Move up dependency versions in user guide

Move up the version numbers of the following Trusted Firmware
dependencies in the user guide:

*   Foundation and Base FVPs (latest publically available
    versions).

*   EDK2 implementation. The guide now uses the latest version from
    https://github.com/ARM-software/edk2.git. This requires the
    `iasl` package to also be installed.

*   Linux kernel. The guide now uses the latest version from
    https://github.com/ARM-software/linux.git.

*   Linaro OpenEmbedded file system.

*   ARM Development Studio 5.

Change-Id: I95bb863a61e47b9ef8be3d110f7087375ee78add
Merge pull request #198 from danh-arm/dh/move-up-dependencies

Move up dependency versions in user guide
Add information about Juno in firmware-design.md

This patch reorganizes the firmware design guide to add information about the
port of the ARM Trusted Firmware to the Juno ARM development platform.

Change-Id: I0b80e2e7a35ccad1af2e971506cfb7fe505f8b84