TBB: rework cert_create tool to follow a data driven approach ...

This patch reworks the certificate generation tool to follow a data
driven approach. The user may specify at build time the certificates,
keys and extensions defined in the CoT, register them using the
appropiate macros and the tool will take care of creating the
certificates corresponding to the CoT specified.

Change-Id: I29950b39343c3e1b71718fce0e77dcf2a9a0be2f

TBB: add tool to generate certificates ...

This patch adds a tool that generates all the necessary elements
to establish the chain of trust (CoT) between the images.

The tool reads the binary images and signing keys and outputs the
corresponding certificates that will be used by the target at run
time to verify the authenticity of the images.

Note: the platform port must provide the file platform_oid.h. This
file will define the OIDs of the x509 extensions that will be added
to the certificates in order to establish the CoT.

Change-Id: I2734d6808b964a2107ab3a4805110698066a04be

Update .gitignore ...

This patch updates .gitignore file to ignore potential build products,
tool object files and binaries

Also fixes issue ARM-software/tf-issues#35

Change-Id: I053dfba4ec8fecbcca081cad5b4bf94f8abfb15c

Build system: Add cscope target to the Makefile ...

Fixes arm-software/tf-issues#15

Signed-off-by: Joakim Bech <joakim.bech@linaro.org>