Bump to development version 19.pre (#2876)

Bump to version 19.pre. We should consider to update the versions of the
server and the web UI.

Author: imobachgs

live/src/agama-installer.kiwi

@@ -17,7 +17,7 @@
         <profile name="SUSE_SLE_16" description="SLE-based image" import="true" />
     </profiles>
     <preferences>
-        <version>18.pre.0.0</version>
+        <version>19.pre.0.0</version>
         <packagemanager>zypper</packagemanager>
         <locale>en_US</locale>
         <keytable>us</keytable>

service/Gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    agama-yast (17.devel904.666a28170)
+    agama-yast (19.pre)
       cfa (~> 1.0.2)
       cfa_grub2 (~> 2.0.0)
       cheetah (~> 1.0.0)