Revert "Add tutorial and user doc. (#4)"

This reverts commit d192a75.

.gitignore

@@ -1,11 +1,3 @@
-build/
-.idea/
-cmake-build-*
-.vscode/
-/.vs
-/doc/impl_doc_cn.md
-/doc/impl_doc.md
-/doc/images
 # Prerequisites
 *.d
 

CMakeLists.txt

@@ -46,11 +46,4 @@ if (BUILD_TESTING)
     add_subdirectory(extern/gtest)
     add_executable(dbtest ${TEST_SOURCES})
     target_link_libraries(dbtest PUBLIC engine gtest gmock gtest_main)
-endif ()
-
-option(BUILD_TUTORIAL "Build the tutorial" ON)
-if (BUILD_TUTORIAL)
-    set(TUTORIAL_SOURCES examples/tutorial.cpp)
-    add_executable(dbtutorial ${TUTORIAL_SOURCES})
-    target_link_libraries(dbtutorial PUBLIC engine)
 endif ()