create auto backup for bookmarks.
move getFileBackup method.
Show last backup date in bookmark activity.
Add dialog to allow user to choose backup file.
Do not show dialog if no files found.
Fix regex for autobackup files.
sort files by name.
Bookmark activity: last backup shown below all bookmarks.
limit autobackup up to 10 files only.
manual backup file is listed on top.
Fix date displayed. Consistent with bookmark activity.
replace string with string resource.
Reverse file ordering.
Add title and add margins.
Change date formating at sqlitil to use format according to user settings
and use threadlocal for safety
Rename strings
Small fixes on BackupManager class
Merge branch 'feature/automatic_backup' into develop

Conflicts:
	Alkitab/res/values/strings.xml
	Alkitab/src/yuku/alkitab/base/ac/BookmarkActivity.java