ComicBook-related renames

What was formerly known as a 'ComicBook' represents a series (issues +
TPB volumes) of comic books. Comic Book-related classes (and one
property) were renamed to reflect this.

Renamed 'ComicBook' class to 'ComicBookSeries'

Renamed 'ComicBookIssue' class to 'ComicBookSeriesEntry'

Renamed 'ComicBookSummary.IssuesCount' to 'EntriesCount'

Renamed test classes.
Renamed resource string related to EntriesCount