GitLab

PEM/DER casting removed, allowing  mbedtls to manage
certificate conversion by itself. Credresource loads
certificates that could be either PEM or DER encoded
to a linked list instead of pushing them to a buffer.

Change-Id: I200f9ef8798b20bf894b8ef2cf85e42e13749f38
Signed-off-by: Oleksii Beketov <ol.beketov@samsung.com>