Added ListedImages and made RtImages abstract

[amihaiemil]

PR for #144

RtImages is abstract since we will have at least 2 implementations: ListedImages and SearchedImages, which will be iterated differently (use a different HTTP endpont).

Left a few puzzles for continuing implementation in different areas.

[0crat]

Job #151 is now in scope, role is REV

[coveralls]

Pull Request Test Coverage Report for Build 284

• 13 of 13 (100.0%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.3%) to 83.153%

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Totals
Change from base Build 280:	0.3%
Covered Lines:	385
Relevant Lines:	463

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💛 - Coveralls

[amihaiemil]

@rultor merge pls

[rultor]

@rultor merge pls

@amihaiemil OK, I'll try to merge now. You can check the progress of the merge here

[rultor]

@rultor merge pls

@amihaiemil Done! FYI, the full log is here (took me 3min)

[0crat]

Job gh:amihaiemil/docker-java-api#151 is not assigned, can't get performer

[0crat]

The job #151 is now out of scope