Qt GUI updates #539

Some important (and less important) updates for the Qt UI

Core:

• use median filter (CMedianFilter) for peer-reported reported number of blocks
  • this fixes problem that one misconfigured or malicious node can mess up progress bar
  • implementation in src/util.h
  • testcase in src/test/util_tests.cpp

UI:

• Translation handling
  • Include translations as resource, so that they are included in the executable. This saves a lot of hassle on installation (less files to worry about), and is similar to how other Qt applications do it
  • In resources, use nl_NL format instead of nl, so that the correct translation is chosen based on system locale automatically
• Improve send coins screen
  • Add balance to remind users how much they can send
  • No longer clear input when switching tabs; this is non-intuitive and can cause loss of work. Instead, add a "clear input" button.

Build system (qmake):

• Add BOOST_LIB_SUFFIX option to make it possible for distribution install scripts (such as Gentoo) to pass in alternative boost library version names without resorting to sed hacks
• Factor out windows/mac specific include, lib paths so that they can be overridden (overall result is still the same)
• Dependency library locations can be customized with BOOST_INCLUDE_PATH, BOOST_LIB_PATH, BDB_INCLUDE_PATH, BDB_LIB_PATH, OPENSSL_INCLUDE_PATH and OPENSSL_LIB_PATH respectively
• Build translations (.qm) automatically in make, no need to run lrelease separately anymore

Minor:

• Add Q_OBJECT everywhere it should be according to Qt rules (removes warnings when lupdate parses sources)
• Use USE_DBUS define instead of QT_DBUS to switch Linux notification mode, to prevent conflicts in some Qt versions
• Update OTHER_FILES section in Qt creator so that all documentation is shown, now that both projects have been fully merged