Implement some helper methods

Correctly add payment methods to Request class.

Add donation section to readme.

[skip ci]

Clean up DB code

Update README.md

No functionality changes.

Fixed "s" missing from the broken getUpdate link in the index.

Make sure there are only uniquely named parameters.

Bot API 3.3

Bot API 3.2

Use unique parameters for SQL query

Also save IDs as string, like in #520

Fix for #596