Some cmake tweaks

[tri4ng1e]

0. added module Findsqlite (if no sqlite found, cmake will stop with error)
1. renamed library from sqlite to ++sqlite and cmake vars from SQLITE... to XXSQLITE
2. added cmake vars XXSQLITE_INCLUDE_DIRS and XXSQLITE_LIBRARIES for easy integration as git submodule
3. removed header files from XXSQLITE_SOURCE_FILES