Description of the Changes

1. Add textAlign: string (left/right/center) property to config.text.textStyle;
2. Remove align option form config.text.textTrackDisplaySetting;
3. Remove forceCenter option from config.text
4. upd documentation;
5. handle caption alignment based on config.text.textStyle.textAlign configuration;
6. upd tests;

CheckLists

• changes have been done against master branch, and PR does not conflict
• new unit / functional tests have been added (whenever applicable)
• test are passing in local environment
• Travis tests are passing (or test results are not worse than on master branch :))
• Docs have been updated