ARROW-5748: [Packaging][deb] Add support for Debian GNU/Linux buster

It'll be released 2019-07-06.

Author: Sutou Kouhei <kou@clear-code.com>

Closes #4709 from kou/packages-debian-buster and squashes the following commits:

f21f0397 <Sutou Kouhei>  Add support for Debian GNU/Linux buster
diff --git a/install.md b/install.md
index 357b15ea..ea3e6fa 100644
--- a/install.md
+++ b/install.md
@@ -91,14 +91,37 @@
 Apache Arrow GLib (C). Here are supported platforms:
 
 * Debian GNU/Linux stretch
-* Ubuntu 14.04 LTS
+* Debian GNU/Linux buster
 * Ubuntu 16.04 LTS
 * Ubuntu 18.04 LTS
 * Ubuntu 18.10
+* Ubuntu 19.04
 * CentOS 6
 * CentOS 7
 
-Debian GNU/Linux:
+Debian GNU/Linux buster:
+
+```shell
+sudo apt update
+sudo apt install -y -V apt-transport-https curl gnupg lsb-release
+sudo curl --output /usr/share/keyrings/apache-arrow-keyring.gpg https://dl.bintray.com/apache/arrow/$(lsb_release --id --short | tr 'A-Z' 'a-z')/apache-arrow-keyring.gpg
+sudo tee /etc/apt/sources.list.d/apache-arrow.list <<APT_LINE
+deb [arch=amd64 signed-by=/usr/share/keyrings/apache-arrow-keyring.gpg] https://dl.bintray.com/apache/arrow/$(lsb_release --id --short | tr 'A-Z' 'a-z')/ $(lsb_release --codename --short) main
+deb-src [signed-by=/usr/share/keyrings/apache-arrow-keyring.gpg] https://dl.bintray.com/apache/arrow/$(lsb_release --id --short | tr 'A-Z' 'a-z')/ $(lsb_release --codename --short) main
+APT_LINE
+sudo apt update
+sudo apt install -y -V libarrow-dev # For C++
+sudo apt install -y -V libarrow-glib-dev # For GLib (C)
+sudo apt install -y -V libarrow-flight-dev # For Flight C++
+sudo apt install -y -V libplasma-dev # For Plasma C++
+sudo apt install -y -V libplasma-glib-dev # For Plasma GLib (C)
+sudo apt install -y -V libgandiva-dev # For Gandiva C++
+sudo apt install -y -V libgandiva-glib-dev # For Gandiva GLib (C)
+sudo apt install -y -V libparquet-dev # For Apache Parquet C++
+sudo apt install -y -V libparquet-glib-dev # For Apache Parquet GLib (C)
+```
+
+Debian GNU/Linux stretch:
 
 ```shell
 sudo apt update
@@ -119,6 +142,7 @@
 sudo apt update
 sudo apt install -y -V libarrow-dev # For C++
 sudo apt install -y -V libarrow-glib-dev # For GLib (C)
+sudo apt install -y -V libarrow-flight-dev # For Flight C++
 sudo apt install -y -V libplasma-dev # For Plasma C++
 sudo apt install -y -V libplasma-glib-dev # For Plasma GLib (C)
 sudo apt install -y -V libgandiva-dev # For Gandiva C++
@@ -140,6 +164,7 @@
 sudo apt update
 sudo apt install -y -V libarrow-dev # For C++
 sudo apt install -y -V libarrow-glib-dev # For GLib (C)
+sudo apt install -y -V libarrow-flight-dev # For Flight C++
 sudo apt install -y -V libplasma-dev # For Plasma C++
 sudo apt install -y -V libplasma-glib-dev # For Plasma GLib (C)
 sudo apt install -y -V libgandiva-dev # For Gandiva C++
@@ -174,25 +199,6 @@
 sudo apt install -y -V libparquet-glib-dev # For Apache Parquet GLib (C)
 ```
 
-Ubuntu 14.04 LTS:
-
-```shell
-sudo apt update
-sudo apt install -y -V apt-transport-https curl gnupg lsb-release
-curl https://dist.apache.org/repos/dist/dev/arrow/KEYS | sudo apt-key add -
-sudo tee /etc/apt/sources.list.d/apache-arrow.list <<APT_LINE
-deb [arch=amd64] https://dl.bintray.com/apache/arrow/$(lsb_release --id --short | tr 'A-Z' 'a-z')/ $(lsb_release --codename --short) main
-deb-src https://dl.bintray.com/apache/arrow/$(lsb_release --id --short | tr 'A-Z' 'a-z')/ $(lsb_release --codename --short) main
-APT_LINE
-sudo apt update
-sudo apt install -y -V libarrow-dev # For C++
-sudo apt install -y -V libarrow-glib-dev # For GLib (C)
-sudo apt install -y -V libplasma-dev # For Plasma C++
-sudo apt install -y -V libplasma-glib-dev # For Plasma GLib (C)
-sudo apt install -y -V libparquet-dev # For Apache Parquet C++
-sudo apt install -y -V libparquet-glib-dev # For Apache Parquet GLib (C)
-```
-
 CentOS:
 
 ```shell