Fix issues with Nepali layouts

- Added the missing ZWNJ/ZWJ key
- Fix a wrong letter in the shift layout of Nepali Romaized layout
- Put the currency symbol for Nepalese Rupee
- Fix the missing 2nd symbols layout
- Use the Devanagari numbers just like Hindi layout
- Fix the Main/Symbols switch key label just like Hindi layout

bug: 6910787
bug: 9833890
Change-Id: Ie6aa5a06008f1e9347d4fc08ededd48287df5d73