Fix #222: Stop showing quotes in dialog text when deleting untitled draft

Fix #222. Check if draft to be deleted has a non-empty title before
showing quotes and the title name in the dialog text.
Tag tables restructured to use tag/tag_type as primary key, lots of work left to do in order to support this new structure
Renamed topic variables/comments to tags
Moved ReaderTagType to its own class file
Added tag_type column to tbl_post_tags
Added tag_type wherever tag data is accessed
Code style cleanup, fixed bug that caused reader tag type to be saved as wrong type in prefs
Simplified DataRequestedListener
Adding/removing tags no longer uses just the tag name
Simplified adding/deleting a tag
Further simplified adding/deleting a tag
Adding a tag with the same name as a default tag now works
Moved db endpoint lookup to ReaderTagTable
Added code for tag preview backstack (issue #1492, PR #1496)
Fixed bug that could cause unwanted post list animation
Row animation no longer occurs for tag preview
Rewrote code created in PR #1498 so application log shows partial (obscured) tag names
Cleanup based on code analysis
Merge branch 'develop' of https://github.com/wordpress-mobile/WordPress-Android
Fix #1503 - removed jank when slowly scrolling blog preview