Revert "Disable payment protocol pending further assessment and potential rework."

This reverts commit 5967654730541a5598cb6005d7a05ef744efebc0.

Conflicts:

	src/qt/bitcoin.cpp
[Qt] ensure payment request network matches client network

- replaces checks in SendCoinsDialog::handlePaymentRequest() that belong
  to PaymentServer (normal URIs are special cased, as only an isValid
  check is done on BTC addresses)
- prevents the client to handle payment requests that do not match the
  clients network and shows an error instead (mainly a problem with
  drag&drop payment requests onto the client window)
- includes some small comment changes also
don't send feeless transactions

(cherry picked from commit 9a2f7a86fca6e243db7745cb1b15b35ce1b97b2e)
Revert "remove unit tests for new fee mode"

This reverts commit 78ed897c4adf021c30cdf10eebf4663f12f78fd1.
remove unit tests for old fee mode
adapt rpc tests to mandatory fees
Update bitcoin_ko_KR.ts

Reflect changes of "src/qt/locale/bitcoin_en.ts" (<location line=""/> included.) and translate All. but It's not perfect.

Question: Am I doing the right way? if not, please 'closed' and give me some advice.
Revised payment request handling to use genesis block hash instead of network name.
Merge pull request #559 from nameEO/patch-1

Update bitcoin_ko_KR.ts
Merge pull request #553 from leofidus/1.7-nozerofee

Don't send feeless transactions
Merge pull request #560 from rnicoll/1.7.2-dev-payment

Re-enable payment protocol