Subsume waitForCompletion/updateDBKeyspace into BlockingCommandOptions

[sl-at-ibm]

Fixes #127 .
More specifically, this PR solves the issue of multiple/opaque bool params to {Create/Drop} x {Database/Keyspace}.

• a subclass BlockingCommandOptions of CommandOptions, used in those methods
• which contains a waitForCompletion boolean (defaulting to true)
• Moreover: reordered (the remaining) implementations for uniformity
• Moreover: breaking change brought the "replication options" at the end of the signature for HCD's CreateKeyspace for uniformity
• Moreover: rephrase/rearrange xmldocs (use "inheritfrom", improve param description, presence/absence of code examples and such)
• Moreover: DropDatabase is not a bool anymore, rather a void, as its semantics would (also DropKeyspace and other clients work like that) (slight) breaking change
• (Some tests renamed and slightly reformulated, also some comments therein)

[the following part outdated, see further posts]
Now I did not subsume updateDbKeyspace into these options... yet. I am not 100% sure this should be done at all:

1. it's only one boolean (still 'opaque', but just one)
2. Its meaning is not really that of "an option that controls request execution" to be strict (like the rest of BlockingCommandOptions is)
3. keeping it top-level saves the quick, easy HCD one-liner "create keyspace and have the DB set to use it". Otherwise it would get a tad more verbose.

@toptobes any opinion?

[sl-at-ibm]

@a-random-steve FYI

[sl-at-ibm]

Note for posterity. Considering the fact that you can anonymously instantiate in the argument (i.e. new() {...} without class name explicitly), and hence the HCD create-and-use-keyspace pattern stays rather terse, it was decided to subsume updateDbKeyspace as well. Which I'm going as a follow-up in this branch - stay tuned.

[sl-at-ibm]

And here we go with the updateDBKeyspace gone into the options as well.

@skedwards88 breaking change. Please note that the "HCD create-and-use" pattern remains short, as exemplified in DatabaseAdminAstra_CreateKeyspaceAsync_Update by the idiom:

await daa.CreateKeyspaceAsync(keyspaceName, new () {updateDBKeyspace = true});