deactivating optional build settings

I deactivated the optional build settings in the main `CMakeLists.txt`.

These are mostly options for developers of SQLiteCpp and not needed by the average user of the library.
I am including SQLiteC++ as a git submodule and then simply adding it to the build script with:

```cmake
 add_subdirectory(ext/SQLiteCpp)                                        
 include_directories("${PROJECT_SOURCE_DIR}/ext/SQLiteCpp/include")
```

This however brings along unnecessary build dependencies to my project which I would like to avoid. Thus I had to change my build script to:

```cmake
 set(SQLITECPP_BUILD_TESTS OFF)                                         
 set(SQLITECPP_BUILD_EXAMPLES OFF)                                      
 set(SQLITECPP_RUN_DOXYGEN OFF)                                         
 set(SQLITECPP_RUN_CPPCHECK OFF)                                        
 set(SQLITECPP_RUN_CPPLINT OFF)                                         
 add_subdirectory(ext/SQLiteCpp)                                        
 include_directories("${PROJECT_SOURCE_DIR}/ext/SQLiteCpp/include")
```

In my opinion this can be avoided by not turning the optional build settings on.
Please consider this pull request, to make your library more light weight in it's default format.

Thanks!