i18n: plural&msg refactoring | + fest_global_variables

* i18n:msg: added 'values' attribute (can contain ',' separated list of
js-expressions - each item in this list will replace '%s' in given
string)
* i18n:plural: value of 'select' attribute will be used to replace the
first occurrence of the '%d' (instead of '%s')
* i18n:plural: added 'values' attribute (same as in i18n:msg)
* i18n:plural: added 'output' attribute with values "json" and
"function" (default value is "")
** i18n:plural with output='json' would contain Plural-Forms function in
'plural' property
+ '__fest_global_vars__' and createFestGlobalVariables method

Note: without tests