Deprecate more features in preparation for 2.0

[alcaeus]

Q	A
Type	improvement
BC Break	no

Summary

After #1924, this adds some more deprecations for 2.0:

• Deprecate partial discriminator maps; references must now define all possible classes in discriminator maps if they have a map (Exception when persisting class unlisted in disciminator map (Issue 867) #1887)
• Deprecate the eagerCursor helper in Query\Builder and the eager option in Query\Query (Remove eager cursor functionality without replacement #1902)
• Deprecate the @NotSaved annotation (Throw exception on duplicate database names within a document #1903)
• Deprecate multiple fields with the same name in the database (Throw exception on duplicate database names within a document #1903)
• Deprecate using multiple class-level document annotations in mappings (Forbid mapping class by more than one AbstractDocument #1906)
• Deprecate timeout option in schema commands (Separate index creation options from index options #1910)
• Deprecate dropDups option in indexes (Separate index creation options from index options #1910)
• Deprecate indexOptions arguments in SchemaManager (Separate index creation options from index options #1910)

[malarzm]

Awesome 🎉