rename useDatabase to useMysqlDatabase and mark useDatabase as as deprecate and support postgresDatabase

[ilyaskarim]

• Remove mysql2 from package.json
• Remove pg from package.json if exists
• Write a method in utils that checks if a specific package is installed or not, there is already a method defined here

  wertik-js/src/framework/initialization/checkInstalledPackages.ts

  Line 3 in 20c91a0

  export function checkIfPackageIsInstalled(packageName: String) {

• When using useMysqlDatabase please check for mysql2 package
• When using usePostgresDatabase please check for pg package by using that package.
• You can write a better version of the above package checking function in the next folder if you want.
• Update documentation
• Confirm relationships work
• Confirm relationships work in graphql
• Confirm take backup works