Bug/01 amount input

This PR include fixes related with SendPage

- Minor fixes (amount input) fixes #751 : 
  * Allow enter values minor than 1 (one).
  * Apply 4 decimal filter. Please, check this bug #758 
  * The directive enoughAmount concatenates the values ​​instead of adding them. So force it to Number type.

- Bug on chrome (not copy value to input field) fixes #741 :
  * Fix copy value and set $pristine to false.
  * Improve styles.

- New tests for new methods and improved test for checking enoughAmount.
groso! $compile()