QT_NO_KEYWORDS prevents Qt from defining the `foreach`, `signals`,
`slots` and `emit` macros.
Avoid overlap between Qt macros and boost - for example #undef hackiness
in #6421.
- remove btc address length from address validator
- add an optional btc address check in validated line edit that defaults
to off and is used in GUIUtil::setupAddressWidget()
- an isAcceptable() check is added to validated line edit on focus out
which only kicks in, when a validator is used with that widget
- remove an isAcceptable() check from sendcoinsentry.cpp
- remove obsolete attributes from ui files, which are set by calling
GUIUtil::setupAddressWidget()
- move some more things to GUIUtil::setupAddressWidget() and remove them
from normal code e.g. placeholder text
- 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
