trust_list: Add OID info/filtering

Package Control will be switching to use oscrypto.trust_list for TLS trust roots to solve:

• https://github.com/wbond/package_control/issues/1002
• https://github.com/wbond/package_control/issues/1079

In order to do this, we need to tweak trust_list.get_list(). Ideally we need:

1. A way to filter get_list() by one or more key usage strings/extended key usage OIDs
2. A new method such as get_list() that will return the list os trust roots along with a set() of their key usage names and extended key usage OIDs

[wbond]

As of 41cb25705aabe33003c89dcc307c81cb23ee650b, oscrypto.trust_list now includes trust information for each certificate in the store, and trust_list.get_path() encodes the trust info into a format that OpenSSL understands.

[ipv6freely]

@FichteFoll Thank you!