Update git submodules

* Update plugins/codemirror-editor from branch 'master'
  to 1f3978dd6b038ca07f5514d23689ede3edc94403
  - Use json from legacy-modes
    
    It seems that json is better highlighted under the legacy modes then
    the modern lang-json package. We'll switch to legacy-modes for json
    for now until it is fixed.
    
    Change-Id: I53859c6d0343059470012e5dd836e3530aa0fbb0

Author: paladox