CMake: Only require needed boost components, Adjust dependency list

Swiften still requires most boost libraries, but kaidan itself only needs
boost signals, now. The dependency list in the README is still very long.
This is because the swiften (-dev) package in debian has not all needed
depends, so we have to add them in our list... :/

CMakeLists.txt

 cmake_minimum_required(VERSION 2.8.11)
 set(CMAKE_CXX_STANDARD 14)
 set(QT_MIN_VERSION "5.7.0")
+set(BOOST_MIN_VERSION "1.34.1")
 
 project(kaidan)
 
@@ -52,7 +53,7 @@ set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_SOURCE_DIR}/cmake")
 find_package(Qt5 ${QT_MIN_VERSION} REQUIRED NO_MODULE COMPONENTS Core Qml Quick Sql)
 find_package(KF5Kirigami REQUIRED)
 find_package(Swiften REQUIRED)
-find_package(Boost REQUIRED)
+find_package(Boost ${BOOST_MIN_VERSION} REQUIRED COMPONENTS signals)
 include(GNUInstallDirs)
 
 #
@@ -87,8 +88,8 @@ target_link_libraries(${PROJECT_NAME}
 	Qt5::Sql
 	Qt5::Qml
 	Qt5::Quick
+	Boost::signals
 	${SWIFTEN_LIBRARY}
-	${Boost_LIBRARY}
 )
 
 #

README.md

@@ -17,7 +17,7 @@ Create a working directory
 
 Install dependencies to build Kaidan (example for Debian)
 
- *  `sudo apt-get install git-core cmake build-essential libstdc++-5-dev zlib1g-dev libglib2.0-dev libssl-dev libxml2-dev libcrypto++-dev libpthread-stubs0-dev libidn11-dev libminiupnpc-dev libnatpmp-dev libswiften-dev libboost-signals-dev libboost-system-dev libboost-thread-dev libboost-regex-dev libboost-program-options-dev libboost-filesystem-dev libboost-serialization-dev libboost-date-time-dev libqt5quick5 libqt5quickcontrols2-5 libqt5quickparticles5 libqt5quickwidgets5 libqt5qml5 libqt5network5 libqt5gui5 libqt5core5a qtdeclarative5-dev qttools5-dev qt5-default qml-module-qtquick-controls2 qml-module-org-kde-kirigami`
+ *  `sudo apt-get install git-core cmake build-essential zlib1g-dev libglib2.0-dev libssl-dev libxml2-dev libcrypto++-dev libpthread-stubs0-dev libidn11-dev libminiupnpc-dev libnatpmp-dev libswiften-dev libboost-system-dev libboost-program-options-dev libboost-serialization-dev libqt5quick5 libqt5quickcontrols2-5 libqt5quickwidgets5 libqt5qml5 libqt5gui5 libqt5core5a qtdeclarative5-dev qttools5-dev qt5-default qml-module-qtquick-controls2 qml-module-org-kde-kirigami`
 
 Get Kaidan source code