Alias code cleanup

- Renamed IndexMetaData#removerAlias to removeAlias
- Removed IndexTemplateMetaData#fromXContentStandalone unused method (relates to #4511)
- MetaDataIndexAliasesService fix typo in comment
- Alias removed unused constructor that accepts both alias name and filter
[TEST] Added tests for alias filter that is valid json but not a valid filter
Added script to extract release notes

Just call ./es_release_notes.pl <issue-tag> to get all release notes.

By default html output is returned, but you can switch to markdown by calling
./es_release_notes.pl <issue-tag> markdown
[DOCS] Fixed typo in create index api