Fix JC-1760:
Error messages for empty 'Username' and 'Password' fields should be in the same style
Error message for empty 'Password' field should be 'Password length must be between 1 and 50 characters' instead of 'Must not be empty'

Fix full error JC-1760:
Sign Up: Error messages in 'Username' and 'Password' fields must be the same

JC-1760
Added new annotation NotBlankSize and new validator NotBlankSizeValidator
Changed UserDto

JC-1760:
Hardcode values ​​in properties files

JC-1760
Corrected 0 to 1 in the message
Merge branch 'master' of github.com:jtalks-org/jcommune into JC-1760
JC-1760
Wrote a new annotation and validator to it to check for a null value and on the size of the string, wh ich must be between the maximum and minimum
Remove user.username.empty and user.password.empty from ValidationMessages_en.properties, ValidationMessages_ru.properties, ValidationMessages_uk.properties
JC-1760
Changed the name of the files SizeOrNull and SizeOrNullValidator on SizeAndNotBlank and SizeAndNotBlankValidator
Written unit test for the validator SizeAndNotBlankValidator
Merge branch 'JC-1760'