Build modified streamline images

The official image from streamline does not currently work for the arm64
platform. As a temporary measure, the source code and docker build scripts
have been lifted from the official images and are used to build locally.

Some additional modifications are made to reduce overall image size, these
are documented in docker/README.md

docker/streamline-src/vendor/knplabs/knp-snappy/appveyor.yml

@@ -0,0 +1,53 @@
+build: false
+platform: x64
+clone_folder:  c:\projects\snappy
+
+environment:
+  matrix:
+    - dependencies: lowest
+      php_ver_target: 7.1
+    - dependencies: current
+      php_ver_target: 7.2
+    - dependencies: highest
+      php_ver_target: 7.3
+
+cache:
+  - composer.phar
+  - c:\ProgramData\chocolatey\bin -> appveyor.yml
+  - c:\ProgramData\chocolatey\lib -> appveyor.yml
+  - c:\php -> appveyor.yml
+
+init:
+  - SET PATH=c:\Program Files\OpenSSL;c:\tools\php;%PATH%
+  - SET COMPOSER_NO_INTERACTION=1
+  - SET PHP=1
+  - SET ANSICON=121x90 (121x90)
+
+install:
+  - IF EXIST c:\tools\php (SET PHP=0)
+  - ps: Set-Service wuauserv -StartupType Manual
+  # In order to be able to list all the avialable PHP packages we have to
+  # downgrade Chocolatey to version 0.10.13.
+  # See https://github.com/chocolatey/choco/issues/1843
+  - ps: choco install chocolatey -y --version 0.10.13 --allow-downgrade --force
+  - ps: choco search php --exact --all-versions -r
+  - ps: echo ((choco search php --exact --all-versions -r | select-string -pattern $env:php_ver_target | sort { [version]($_ -split '\|' | select -last 1) } -Descending | Select-Object -first 1) -replace '[php|]','')
+  - ps: appveyor-retry cinst php --params '""/InstallDir:c:\tools\php""' --ignore-checksums -y --force --version ((choco search php --exact --all-versions -r | select-string -pattern $env:php_ver_target | sort { [version]($_ -split '\|' | select -last 1) } -Descending | Select-Object -first 1) -replace '[php|]','')
+  - cd c:\tools\php
+  - IF %PHP%==1 copy php.ini-production php.ini /Y
+  - IF %PHP%==1 echo date.timezone="UTC" >> php.ini
+  - IF %PHP%==1 echo extension_dir=ext >> php.ini
+  - IF %PHP%==1 echo extension=php_openssl.dll >> php.ini
+  - IF %PHP%==1 echo extension=php_mbstring.dll >> php.ini
+  - IF %PHP%==1 echo extension=php_fileinfo.dll >> php.ini
+  - IF %PHP%==1 echo @php %%~dp0composer.phar %%* > composer.bat
+  - appveyor-retry appveyor DownloadFile https://getcomposer.org/composer.phar
+  - cd c:\projects\snappy
+  - IF %dependencies%==lowest appveyor-retry composer update --prefer-lowest --no-progress --profile -n
+  - IF %dependencies%==current appveyor-retry composer install --no-progress --profile
+  - IF %dependencies%==highest appveyor-retry composer update --no-progress --profile -n
+  - composer show
+
+test_script:
+  - cd c:\projects\snappy
+  - vendor/bin/phpunit