Password input

Sistema provides a password input field displaying a password input and a button allowing to show/hide the password.

`nsi-password-input` is extending `NativeTextFieldDirective` meaning it's working well with both Angular `FormModule` and `ReactiveFormModule` .

Password
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### Inherited from `PaFormControlDirective`

### Inherited from `NativeTextFieldDirective`

`nsi-password-input` is extending `NativeTextFieldDirective` but some of the Inputs inherited from it doesn't make sense in the context of a password field. Here's the list of Inputs which have an effect on `nsi-password-input` :

#### Inputs

errorMessages
  Provides default messages to display for the possible error keys when none is present in the errors object. If a message (string) is provided for a given key, it will be displayed rather than the message provided in errorMessages.
hasFocus
  triggers the focus on the input field (optional)
help
  A hint to display, helping the user when filling a form field (optional)
placeholder
  Field's placeholder (optional)
showAllErrors
  Display all errors or only the first error encountered (errors being sorted by key) (default: true)

#### Outputs

keyUp
  Emits `string` value on key up event
enter
  Emits `KeyboardEvent` and `string` value when pressing enter
focusing
  Emits `FocusEvent` on focus
blurring
  Emits current value on blur

Password input is working well with both Angular FormModule and ReactiveFormModule.

ngModel example:

    {{ngModelCode}}

FormControl example:

    {{formControlCode}}

FormGroup example:

    {{formGroupCode}}