fiptool: Add support for printing the sha256 digest with info command ...

This feature allows one to quickly verify that the expected
image is contained in the FIP without extracting the image and
running sha256sum(1) on it.

The sha256 digest is only shown when the verbose flag is used.

This change requires libssl-dev to be installed in order to build
Trusted Firmware. Previously, libssl-dev was optionally needed only
to support Trusted Board Boot configurations.

Fixes ARM-Software/tf-issues#124

Change-Id: Ifb1408d17f483d482bb270a589ee74add25ec5a6

fiptool: Fix typo in create and update usage functions ...

It should be 'fiptool' instead of 'fiptfool'.

Change-Id: I84ce1b6aaae5b8b33e5781bfe4f9e9cf462edb03

Replace fip_create with fiptool ...

fiptool provides a more consistent and intuitive interface compared to
the fip_create program.  It serves as a better base to build on more
features in the future.

fiptool supports various subcommands.  Below are the currently
supported subcommands:

1) info   - List the images contained in a FIP file.
2) create - Create a new FIP file with the given images.
3) update - Update an existing FIP with the given images.
4) unpack - Extract a selected set or all the images from a FIP file.
5) remove - Remove images from a FIP file.  This is a new command that
   was not present in fip_create.

To create a new FIP file, replace "fip_create" with "fiptool create".

To update a FIP file, replace "fip_create" with "fiptool update".

To dump the contents of a FIP file, replace "fip_create --dump" with
"fiptool info".

A compatibility script that emulates the basic functionality of
fip_create is provided.  Existing scripts might or might not work with
the compatibility script.  Users are strongly encouraged to migrate to
fiptool.

Fixes ARM-Software/tf-issues#87
Fixes ARM-Software/tf-issues#108
Fixes ARM-Software/tf-issues#361

Change-Id: I7ee4da7ac60179cc83cf46af890fd8bc61a53330