build: features need to be enabled

For meson we dont just check for the presence of a dependency and
then auto enable it.
Users must enable features explicit. This helps with having
deterministic results.

Also remove the general `plugins` switch which was used to
enable/disable both python and c plugins. Users can just use
those switches.

meson_options.txt

@@ -1,51 +1,77 @@
+# Features:
 option('notifications',
   type: 'feature',
-  value: 'auto',
+  value: 'disabled',
   description: 'Enable desktop notifications'
 )
 
 option('python-plugins',
   type: 'feature',
-  value: 'auto',
+  value: 'disabled',
   description: 'Enable Python plugins'
 )
 
 option('c-plugins',
   type: 'feature',
-  value: 'auto',
+  value: 'disabled',
   description: 'Enable C plugins'
 )
 
-option('plugins',
-  type: 'feature',
-  value: 'auto',
-  description: 'Enable plugins (both Python and C)'
-)
-
 option('otr',
   type: 'feature',
-  value: 'auto',
+  value: 'disabled',
   description: 'Enable OTR encryption'
 )
 
 option('pgp',
   type: 'feature',
-  value: 'auto',
+  value: 'disabled',
   description: 'Enable PGP'
 )
 
 option('omemo',
   type: 'feature',
-  value: 'auto',
+  value: 'disabled',
   description: 'Enable OMEMO encryption'
 )
 
 option('xscreensaver',
   type: 'feature',
-  value: 'auto',
+  value: 'disabled',
   description: 'Use libXScrnSaver to determine idle time'
 )
 
+option('icons-and-clipboard',
+  type: 'feature',
+  value: 'disabled',
+  description: 'Enable GTK tray icons and clipboard paste support'
+)
+
+option('gdk-pixbuf',
+  type: 'feature',
+  value: 'disabled',
+  description: 'Enable GDK Pixbuf support to scale avatars before uploading'
+)
+
+option('omemo-qrcode',
+  type: 'feature',
+  value: 'disabled',
+  description: 'Enable ability to display OMEMO QR code'
+)
+
+# Other:
+option('python_framework',
+  type: 'string',
+  value: '',
+  description: 'Set base directory for Python Framework (macOS only)'
+)
+
+option('tests',
+  type: 'boolean',
+  value: false,
+  description: 'Build tests'
+)
+
 option('install_themes',
   type: 'boolean',
   value: true,
@@ -57,33 +83,3 @@ option('themes_path',
   value: '',
   description: 'Custom path for themes installation (empty for default)'
 )
-
-option('icons-and-clipboard',
-  type: 'feature',
-  value: 'auto',
-  description: 'Enable GTK tray icons and clipboard paste support'
-)
-
-option('gdk-pixbuf',
-  type: 'feature',
-  value: 'auto',
-  description: 'Enable GDK Pixbuf support to scale avatars before uploading'
-)
-
-option('omemo-qrcode',
-  type: 'feature',
-  value: 'auto',
-  description: 'Enable ability to display OMEMO QR code'
-)
-
-option('python_framework',
-  type: 'string',
-  value: '',
-  description: 'Set base directory for Python Framework (macOS only)'
-)
-
-option('tests',
-  type: 'boolean',
-  value: false,
-  description: 'Build tests'
-)