renamed to DI container, complete rework of section "2. Identifiers", ...

+ Identifier section contains new sub section "2.3 Identifier types",
   which replaces the idea of allowing "more then one identifier"
+ marked and explained requirement keywords and fixed some usages
~ refactored some complex expressions to language constructs to ease reading
~ checked the formatting that is defined in the legend to be used correctly
~ reduced reusing words of the same kind for different things as much as possible,
   using synonyms in a consistent way instead