Variadic bind convenience function

[pauldreik]

This gives the possibility to let the compiler generate the index argument in Statement::bind() automatically at compile time, instead of manually invoking bind.
Instead of
SQLite::Statement stmt("SELECT * FROM MyTable WHERE colA>? && colB=? && colC<?"); stmt.bind(1,a); stmt.bind(2,b); stmt.bind(3,c);
one can write
SQLite::bind(stmt,a,b,c);

Note that this is implemented as a free function. It could be provided as a member function of SQLite::Statement instead, under a different name than bind in order not to clash with the existing SQLite::Statement::bind() overloads.

This requires c++14. Tested on gcc 5.3.1 on GNU/Linux.

[coveralls]

Coverage remained the same at 0.0% when pulling 356c50a on pauldreik:master into bf61578 on SRombauts:master.

[SRombauts]

Thanks a lot for this high quality work!