working version 0.1

-UI is based on the block-read Android example
-The development of the DLSignerNfc library began.
-Implemented basic file open, read and digital signature write operations.
-Note: code for digest pre-formatting have to be moved to the DLSignerNfc class because in the case of the ECDSA algorithm it is necessary to read the length of the public key  of which depends the formatting of the digest.