Remove debug code
Don't trust get_folder(), use mailbox environment variable when appropriate
Add plugin hook 'db_table_name' as requested in #1489837
Check available memory for image resizing with GD on Windows (#1489937)
Fix skin path handling in plugin context (#1488967):
The plugin skin directories are removed again from the search path after parsing of a plugin template has finished.
Update changelog
Remove redundant code
Move TNEF decoder class to the Roundcube Framework (#1490055)

So, for now all dependencies of the Framework can be installed
with composer and we need only lib/Roundcube folder.
des.inc was never required and is less important since we do
encryption using openssl or mcrypt extensions.
Remove redundant margin
Add csv2vcard for ru_RU localization
Fix some character sets detection (#1490135)
Add Dockerfile.
Add SSL support to Dockerfile.
Add environment variable reading to configuration.

Docker prefers to pass parameters via environment variables.  This
allows the environment variables to be checked and if a value exists it
will override the default.