finished #14246 http://redmine.ruswizards.com:8100/redmine/issues/14246
added .gitignore
renamed methods which change visibility preferences
rewrited SeekBarPreference according code guide
changed logic of visibility preferences
Merge pull request #13 from eteplyakov/RM_14246_Lab_level_2_Preferences_dynamic

RM14246 - Lab level 2. Preferences (Dynamic)