Validators

Some validators

part1: **Regex based validators**
- matchesPattern (pattern : string)
- isAlphanumeric
- containsAtLeastOneDigit
- containsAtLeastOneUpperCaseCharacter
- containsAtLeastOneLowerCaseCharacter

Might be useful e.g. for password validations:
```
let password = self.Factory.Backing(<@ self.Password @>, "", notNullOrWhitespace >> noSpaces >> containsAtLeastOneDigit >> containsAtLeastOneUpperCaseCharacter >> containsAtLeastOneLowerCaseCharacter >> hasLengthAtLeast 8)
```

part2: **Fixes for generic validators**:
- changed some names to make it consistent with string length validators.
- added `lessThan`
- fixed error messages
- added `isBetween`