Enable custom wallet filename
Add improvements suggested by domob1812
* Qt5 compatibility
* src/net.cpp: fixed miniupnpc issue
Port from Bitcoin: https://github.com/laanwj/bitcoin/commit/61d85071405b99c3734606eed31ea8f615c0c77a#diff-772f489c7d0a32de3badbfbcb5fd200dR553
Fix MinGW build issue and simplify code.
Fix grayed out X-button (close) on Windows with Qt5.
Merge pull request #122 from phelixnmc/Qt5_compatibility

Qt5 compatibility
fix double path in wallet backup
Merge pull request #121 from digital-dreamer/custom-wallet-filename

Custom wallet filename option
changelog.md: walletpath
Disable warnings that flood the output otherwise.
Implement sendtoname in the Qt UI.

Allow entering names into the "Pay To" field in Qt, to mimic the
"sendtoname" functionality.
Update changelog for the patch.