Blockly: improve variables handling
Blockly: improve variables handling

In includedBlocks, two keys for variables:
-variables: ['var1', '*']
  List of variables to generate fixed blocks for
  If '*' is present, generate a non-fixed block (letting the user select the
  variable).

-variablesOnlyBlocks: ['get', 'incr']
  List of blocks to generate for each variable (between 'get', 'set', 'incr').
  If not present, will generate all three blocks.

Moreover, if the category 'variables' is included in
standardBlocks.wholeCategories, it will automatically add '*' to variables.

be-oi/beoi-contest-modules,France-ioi/bebras-modules,France-ioi/bebras-modules,be-oi/beoi-contest-modules