move some shared logic to functions
indent the proper amount
don't do value checks in the numbers
Merge pull request #1125 from reaperhulk/rsa-numbers-with-functions

Move some shared logic to functions
backend specific RSA*Key implementation for OpenSSL
remove skip in serialization tests until we have a backend that needs it
get numbers from loaded keys in numbers test
modify rsa.RSAPrivateKey to build old style key from numbers
remove an unused method
rsa_cdata creation should immediately be registered for gc
simplify test_rsa changes
pkey_size should be private
inline a single use function
do value checks when converting from numbers to key