NPW(New Power Coin) Aug 2019 update

Main updates of the new UI wallet:
1. Fixed the abnormal display issue in MN daily income data;
2. Fixed the problem that the currency price could not be updated correctly.
https://github.com/NPW-Project/npw_walletapp_desktop/releases/download/v2.1.20/NewPowerCoinClient_setup_2.1.20.exe

Main updates of the mobile version:
1. Fixed the problem of misalignment in various types of smartphone in the classification column of transaction records;
2. Repaired OTC exchange price which could not be updated in real time;
3. Improved the timed reward collection rules, and added a QR code to collect rewards;
4. Improved the rewards rules so that more people can receive timed rewards.
https://github.com/NPW-Project/NPW_Mobile/releases/download/v1.1.20/NPW-release-v1.1.20.apk

All features will be ready in the next update of QT wallet.:
1. Receivecoinsdialog: added button for Receiving Addresses, displayed receiving address list. Repaired:
1. GCC-7 and glibc-2.27 compat code.


Optimization:
1. Added GMP bignum;
2. Improved clarity of bignum selection messages;
3. Removed the explicit copy assignment operator from Accumulator.