bump crengine to version cr3-3.1.2-27
build crengine as shared library

* upstream project removed CMakeLists.txt in crengine dir now, so I
added our own in kpvcrlib/CMakeLists.txt

* fix segfault bug in lvimg.cpp by removing JCONFIG_INCLUDED definition
minor tweak for kpvcrlib/CMakeLists.txt
bugfix: always showing ToC of fist opened epub
add screen dpi property in koptcontext
update k2pdfopt to version 1.6.3
add libk2pdfopt as a prerequisite lib for kpdfview object