[Balance sheet] Edit a Balance sheet table entry

**Feature description: A user can edit a balance sheet entry**

Flow:
1. Go to Main menu > "Extrase de cont" > select a _Balance sheet_ from the _Balance sheet list_ / add new _Balance sheet_ > "Intrări și ieșiri"
2. Click on the  (more actions button) on the last column in the table > click on “Editează”.
3. A new page will show, "Editare linie", similar to “Adaugă linie” (issue (https://github.com/code4romania/alex-api/issues/12), where the user needs to edit the prefilled fields.

[Figma mockup](https://www.figma.com/file/W7ppl5xGFpB3atVWwYL7qN/Alex-(asistentul-bugetar-al-ONG-urilor)?node-id=3186%3A39617)

**Actions on Edit a Balance Sheet entry:**
1. Save the changes - the user can press the button “Salvează”.
2. Go back without saving the changes - the user can press the button “Înapoi” from the page header.
3. Reset the fields to their initial prefilled value - the user can to press the button “Resetează”.