Silex replacement

Hey guys, this PR shows up how would looks Silex instead of Slim. Please get it only as an illustration for #34. If it would be accepted, I will refactor some code like separate class Db outside of index.php, etc. The main changes are in configuration and an execution of SQL calls. The rest is nearly the same.

In this example there are not shown advantages Silex against Slim because I haven't used any features, I have only replaced Slim by Silex.

Please let me know what do you think.