language-specific collations: be-tarask added; be, be-tarask, ru verified

Change-Id: I560d766f9b9e9a4ff79e35aa4eec79be875c84c7
adjusted comments for IcuCollation::$tailoringFirstLetters

More information about what actually sits in that array.

Summary of modifications to the Mimer data so far:
* removed data for "traditional" variants of de (German) and es (Spanish)
* used code 'tl' instead of 'fil' for Tagalog/Filipino
* added be-tarask (Belarusian Taraškievica)

Change-Id: I97273c52599a5eda3f63366d697b077d6b17ba81
Merge changes I97273c52,I560d766f

* changes:
  adjusted comments for IcuCollation::$tailoringFirstLetters
  language-specific collations: be-tarask added; be, be-tarask, ru verified