Update versions of dependencies in user-guide.md

1. Update user-guide.md with the latest versions of dependent
components required by the tested configurations of ARM Trusted
Firmware. This includes the tested versions of Fixed Virtual
Platforms (FVPs), toolchain, EFI Development Kit 2(EDK2),
Linux kernel and Linux file system.

2. Remove the instructions to configure the Cortex Base FVP
with the legacy GICv2 memory map as this is no longer supported
since version 5.3 of the Base FVPs.

3. General tidyup of "Using the software" section.

Change-Id: If8264cd29036b59dc5ff435b5f8b1d072dd36ef0
Separate firmware design out of user-guide.md

Move the firmware design documentation out of user-guide.md
and into a new file - firmware-design.md. Reformat the
section headers.

Change-Id: I664815dd47011c7c1cf2202aa4472a8fd78ebb92
Add EL3 runtime services and SPD documentation

1. Add design information on EL3 runtime services and
Secure-EL1 Payload Dispatchers (SPD) to
firmware-design.md.

2. Create new EL3 runtime service writer's guide
(rt-svc-writers-guide.md) to ease creation of new
runtime services.

Change-Id: I670aeb5fc246e25c6e599a15139aac886a0074fd
Consolidate design and porting documentation

Consolidate firmware-design.md and porting-guide.pm so
that recently added sections fit better with
pre-existing sections. Make the documentation more
consistent in use of terminology.

Change-Id: Id87050b096122fbd845189dc2fe1cd17c3003468
Add v0.3 release documentation

Update the readme.md and change-log.md with release information.

Also, remove the "Detailed changes since last release" section of
the change-log.md since the same information can be found in the
GIT commit messages. Fixes ARM-software/tf-issues#22.

Change-Id: I968cc8aaf588aa5c34ba8f1c12a5b797a46e04f5