Qt5 compatibility

This commit squashes all the changes in the Qt5 branch
relative to master.

Backward compatibility with Qt4 is retained.

Original authors:

- Philip Kaufmann <phil.kaufmann@t-online.de>
- Jonas Schnelli <jonas.schnelli@include7.ch>
remove GetBoolArg() fDefault parameter defaulting to false

- explicitly set the default of all GetBoolArg() calls
- rework getarg_test.cpp and util_tests.cpp to cover this change
- some indentation fixes
- move macdockiconhandler.h include in bitcoin.cpp to the "our headers"
  section
Merge pull request #2721 from laanwj/2013_05_qt5

Qt5 compatibility
Merge pull request #2588 from Diapolo/GetBoolArg

remove GetBoolArg() fDefault parameter defaulting to false