Refactor qmake SUBDIRS structure

The big swift.pro is refactored by the correct usage of SUBDIRS
template. The following additional changes are made:
- Removed '_' from all targets and folder names
- Aligned parent folder and target name

refs #461

docs/docs.pro

@@ -0,0 +1,30 @@
+load(common_pre)
+
+TEMPLATE = lib
+CONFIG += staticlib
+CONFIG -= qt
+
+DOXYFILE = Doxyfile.qmake
+
+DOXY_INPUT = .
+win32-g++ {
+	doxy.commands = set DOXY_SRC_ROOT=$$SourceRoot\\src & \
+			doxygen $$PWD/$$DOXYFILE
+}
+else:win32 {
+	doxy.commands = set DOXY_SRC_ROOT=$$SourceRoot\\src & \
+			doxygen $$PWD\\$$DOXYFILE
+}
+else {
+	doxy.commands = DOXY_SRC_ROOT="$$SourceRoot/src" \
+			doxygen $$PWD/$$DOXYFILE
+}
+doxy.CONFIG = no_link target_predeps
+doxy.depends = $$PWD/$$DOXYFILE
+doxy.input = DOXY_INPUT
+doxy.name = DOXY
+doxy.output = html/index.html
+QMAKE_EXTRA_COMPILERS += doxy
+OTHER_FILES += Doxyfile.qmake
+
+load(common_post)