New class for parsing MAL date strings

Add a new class for parsing the different date strings that the API
returns from MAL. This can parse every date format I found for "last
online" and "friends since".

- parseMALDate() parses a date string and returns a Date-object
- parseMALDateToString() parses a date string and returns a complete
  ISO 8601 date string (for storing in database)
Cleanup

Use constants and correct log types, remove debug output.
Add function for date formatting

formatDate() and formatISO8601DateString() can be used to format dates
nicely. This functions will return following formats:

- for dates which are less than a hour ago: "x minutes ago"
- for dates which are less than a day ago: "x hours ago"
- for dates which are less than two days ago: "Yesterday, <Time>"
- for dates which are less than five days ago: "<Dayname>, <Time>"
- everything else will be formatted as <Date>, <Time>

This is completely translatable as resource strings are used.
Rename parse function

Changed to more descriptive name
Don't return unchanged strings

Return an empty string if parsing failed to make error handling
possible.
Rename resources

We'll need also an date only resource, so rename the current resources
to "datetime...".
Added function for direct formatting of MAL date to translated date
Add another dateformat to parseMALDate

The join date has the format "MMMM dd, yyyy", this is now supported too.
Format functions can return date only
Format dates in ProfileActivity
Simplify date formatting

formatDateString now tries to format a ISO 8601 string itself, so this
is not required to be done separately.
Store dates as ISO 8601 strings in database
Ignore case when checking for "now"
Don't save milliseconds
Use new date formatting on FriendsActivity
Remove unneeded function

This one is not needed anymore because of b7995184.
Remove debug lines
There can be more than one whitespace

The dateformat MMMM dd, yyyy can contain more than one whitespace
between month and day.
Don't display time on birthday
Merge pull request #143 from d-sko/date_parsing

Parse dates from MAL