Improve calendar translations in different cultures

Currently, in calendar, it is always string MONTH, YEAR.
But in some languages, month spelling is not the same depending if it's inside a full date (eg. 18 January 2014) and calendar (January, 2014)

For example, in Ukrainian it is 18 січня 2014 fro a date, but it should be "Січень 2014" in calendar (today, it's "січня 2014")

In many language, year should be before month.

The coma is maybe not the best solution, as used in standard date format of many languages.

My proposal is to add new strings for month in calendar, an option (metadata params of xml language file) to set if month before year or year before month, and to give more possibilities for translators to set formatting as it is in their culture (string optional for prefix and/or suffix for month and/or year, and optional separator)

By default, as en-GB the source language, and because no need of prefix or suffix, i have set these strings with a default text, which could help translators using a platform such as Transifex

For example,

en-GB (source) : SUFFIX_MONTH="CALENDAR_SUFFIX_MONTH_FACULTATIVE"
    fr-FR (French) : SUFFIX_MONTH=""
    ja-JP (Japanese) : SUFFIX_MONTH="月"
    and so on...


I've set the separator by default as a space (and remove the comma, not used in some language, and so give possibility to have no space (as for example in Japanese)

So for all prefix, suffix and separator strings, if empty  ( "" ) nothing is displayed.

This PR allows flexibility for translators to set date formatting when use in title of the calendar as it is grammatically correct in their language.