Test Vector changes

Changed names of existing vectors to be more instructive about what the
key contains, and adapted tests to compensate, which pass. Added public
keys for all encryption types and two new private keys for PEM
serialization, documented in the README.txt in the same folder
Update test-vectors.rst

Updated the readme with custom vectors, although formatting errors seem to exist
Update spelling_wordlist.txt

Added some keywords for vector documentation
Updated spelling_wordlist.txt

Updated the spelling list to allow for RSA in the vectors README.
try/finally the bn_ctx manager
Merge pull request #1341 from michael-hart/ec_vectors

Test Vector changes
small cleanup to docs
Merge pull request #1344 from reaperhulk/bn-ctx-fix

start and end BN_CTX so BN_CTX can track func owner of temporary BNs
Merge pull request #1347 from reaperhulk/doc-cleanup

small cleanup to docs
add EC WithNumbers interfaces and docs
Support EC WithNumbers on OpenSSL backend + tests
fix naming mistake in the docs (for DSA and the new EC docs)
refactor to use ctx manager and share logic with set_public_key_affine
extraneous blank line excision