add Kdav (#83)

* add a kdav image
* do not install composer into the docker image
instead use a multi stage build that copies the resulting directory into the final image
* set default version in compose

resolves #54

kdav/apache2-kopano-kdav.conf

@@ -0,0 +1,29 @@
+<VirtualHost *:80>
+    DocumentRoot /usr/share/kdav/
+
+    LogFormat "%{X-Forwarded-For}i %{%a %b %d %T %Y}t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" proxy
+    ErrorLog "|/bin/cat"
+    CustomLog "|/bin/cat" proxy
+
+    RewriteEngine On
+    # redirect well-known url http://sabre.io/dav/service-discovery/
+    # (redirect may need to be done to the absolute external url)
+    RewriteRule ^/.well-known/carddav$ / [R]
+    RewriteRule ^/.well-known/caldav$ / [R]
+    # This makes every request go to server.php
+    RewriteRule ^/(.*)$ /server.php [L]
+
+    # Output buffering needs to be off, to prevent high memory usage
+    php_flag output_buffering off
+
+    # This is also to prevent high memory usage
+    php_flag always_populate_raw_post_data off
+
+    # SabreDAV is not compatible with mbstring function overloading
+    php_flag mbstring.func_overload off
+
+    # set higher limits by default
+    php_value memory_limit 256M
+    php_value max_execution_time 259200
+
+</VirtualHost>