Created Validate class with static methods

Validates:
 * unsigned integers
 * non-empty plain text
 * ip
 * mac
 * directory path
 * name
 * version
 * model
 * username
 * password
 * ssh_username
 * ssh_password
 * os
 * sources

 Throws new ValidateException if not ok.
Added validation in controllers
Removed unnecessary stuff from Request