-Fixed all about saving binary file containing digital signature.
-Fixed error in digest calculation (it was wrong calculated last chunk size)

-Finally base64 encoded signature goes to ebSignature EditText box and you can save it now.
-Implemented FileSelector dialog for "Save As" functionality.

-Updated class DLSignerNfc to v1.1: Digest padding implemented (except when digest is None with RSA)
-Fixed entanglement between mProgressDialog and mSpinnerDialog

-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.