Change DefaultLikeSummaryCreator implementation to use distinctive i18n keys

com.atlassian.confluence.plugins:confluence-like

The com.atlassian.confluence.plugins.like.DefaultLikeSummaryCreator composes sentences for the like summary, afaics these are seven possible sentences (see related issues).

The problem is that the composition approach works for English, and kind of works for German, but we're already in trouble for French. E.g. likes.summary.word.like, which is used for "Vous aimez ça" (You like this) and "2 personnes aimez ça" (2 people like this, but should really be "2 personnes aiment ça"). I'm sure there will be more problems arising when it comes to e.g. the Asian languages.

The correct implementation should be to have distinctive i18n keys for all possible sentences. Redundancy in i18n is a good thing ...