Bitcoin-Qt: massive header and cpp cleanup

- try to enforce the same style to all Qt related files
- remove unneeded includes from the files
- add missing Q_OBJECT, QT_BEGIN_NAMESPACE / QT_END_NAMESPACE
- prepares for a pull-req to include Qt5 compatibility
CheckBlock rule until 15-May for 10,000 BDB lock compatibility
Before 15 May, limit created block size to 500K
Checkpoint at first block in 11 March chain fork
Update unit test to match rule enforcement starts 21 March
Merge pull request #2210 from Diapolo/Qt_header_cpp_cleanup

Bitcoin-Qt: massive header and cpp cleanup