Support RSA public keys and SHA2 signatures

Signed-off-by: Sven Strickroth <email@cs-ware.de>
Use a new 4096 bit RSA public key for update signing

Signed-off-by: Sven Strickroth <email@cs-ware.de>
Merge branch 'RSA'
Prevent possible division by zero

Signed-off-by: Sven Strickroth <email@cs-ware.de>
Export: Add post action Explore To

Signed-off-by: Sup Yut Sum <ch3cooli@gmail.com>