Move Dispathcer example out of com.github.kotlintelegrambot.dispatcher and add required imports

[wesley800]

When I tried to copy-paste the exmaple code to a class under my custom package (other than com.github.kotlintelegrambot.dispatcher), I found that all update subclasses are missing. Meanwhile IDEA just won't give out any import suggestions. I'm new to kotlin and it took quite a few time to find the root cause. Maybe it's better to make the examples more like a standalone project, rather than lies under com.github.kotlintelegrambot?

To be specific, I have to add the below lines if I change the package name in the first line of kotlin-telegram-bot-main/samples/dispatcher/src/main/kotlin/com/github/kotlintelegrambot/dispatcher/Main.kt. Though they are (obviously) not required if package name is com.github.kotlintelegrambot.dispatcher.

import com.github.kotlintelegrambot.dispatcher.message
import com.github.kotlintelegrambot.dispatcher.command
import com.github.kotlintelegrambot.dispatcher.callbackQuery
import com.github.kotlintelegrambot.dispatcher.text
import com.github.kotlintelegrambot.dispatcher.location
import com.github.kotlintelegrambot.dispatcher.contact
import com.github.kotlintelegrambot.dispatcher.channel
import com.github.kotlintelegrambot.dispatcher.inlineQuery
import com.github.kotlintelegrambot.dispatcher.photos
import com.github.kotlintelegrambot.dispatcher.dice
import com.github.kotlintelegrambot.dispatcher.telegramError