Improved Send

[Written by @justindg. More information to come as soon as available.]

Improve overall Send user experience.

Currrent areas of improvement:

- Too many steps needed to get to final confirmation dialog
- Access Send from Bottom Navigation
- Implement token selection from Send screen
- Record the last sent token and move it at the top of the list of token selection
- Dropdown/caret is confusing - it is a fiat/crypto switch, but this UX often signifies token selection
- Text gravity in the amount inputbox is `right`, therefore it moves whenever the user types. This is causes irregular eye movement, which is not good especially the nature of input is considered sensitive
- `All Funds` can be changed to `Max`, a more common term

Android-specific:
- Class hasn't been touched in a while. Refactor the whole class, fix bugs, optimize, and implement TODOs.