- experimental switch of code editor to ACE
 * WARNING : ace source files are NOT included for now, therefore if you want to use this version please put the official ace folder "lib/ace" under assets/libs/ace
for it to work
 * this is merely temporary until the choice of editors is finalized
 * migrated/forked and adapted most of the elements of the codemirror editor to Ace
 * undo redo works, but seems a bit shaky
 * clearing of compile error icons/ lint error icons is not finalized
 * needs some stylesheet cleanup