Change JSON API to accept JSON in URL instead of HTTP body

* Parse out JSON fields from URL instead of HTTP body
* Change RSA pubkey format from hex encoded pem to just pem
* Correct API validation errors
Merge remote-tracking branch 'origin/dev'

* origin/dev:
  working js for T1
  wip t1 prep / pubkey
  working js for T1
  wip t1 prep / pubkey
contract_id being set for t1 / prep page
Remove hex encoding from RSA pubkeys in test setup
Correct ec pubkey length check error message
t1 prep working with backend
Merge branch 'master' of github.com:hdiedrich/mw
wip: sign / wait page depending on T1s
minor readme update
Enable get_contract_t2_state/1 for when contract is not full
Use get_contract_t2_state/1 from prep page handling

* Use get_contract_t2_state/1 to check whether t2 can be signed
* Add temp "contract full" HTML for prep page to avoid generating
  keys when contract cannot be entered
Add hex encoded bitcoin tx signature der encoding validation
t2 sign JS - probably pretty much complete
Merge branch 'master' of github.com:hdiedrich/mw
Correct matching on get_contract_info/1
Add oracle privkey to get-t3-for-signing

* Return plaintext oracle privkey in response to get-t3-for-signing
* Change get-t3-for-signing to take a query string instead of json
* Update oracle_keys table queries and set epgsql worker count to 1
Return encrypted event privkey for get-t3-for-signing
cashout.html, to cashout2.html via GET
wip
Change back get-t3-for-signing to use JSON instead of QS