Fix initialization of RedisOptions and Redis[*]ConnectOptions

[Ladicek]

This commit makes sure that:

• all mandatory fields of RedisOptions are initialized (initializing them only in Redis[*]ConnectOptions is not enough due to the usage of copy constructors);
• all constructors of subclasses of RedisConnectOptions properly delegate to the corresponding superclass constructors;
• the JsonObject-accepting constructors of subclasses of RedisConnectOptions call the correct conversion function, after delegating to the corresponding superclass constructor, which calls its own conversion function.

[vietj]

should we have tests for this @Ladicek ?

[Ladicek]

Good point! Let me figure out some tests for this.

[Ladicek]

Added tests. Thanks for insisting on it, I actually discovered a few more subtle bugs -- most importantly, the JSON serialization/deserialization used to get/set the endpoints list multiple times, due to the existence of multiple getter/setter pairs, and that could actually lead to loss of information.

[vietj]

thank you @Ladicek