DATAMONGO-1025 - Fix creation of nested named index.

We now prefix explicitly named indexes on nested types (eg. for embedded properties) with the path pointing to the property. This avoids errors having equally named index definitions on different paths pointing to the same type within one collection.

Along the way we harmonized index naming for geospatial index definitions where only the properties field name was taken into account where it should have been the full property path.

Deprecated `collection` attribute for `@Indexed`, `@CompoundIndex` and `@GeoSpatialIndexed`.
Removed attribute `expireAfterSeconds` from `@CompoundIndex`.

**Note:** It might happen that one has to explicitly drop some of the already created index structures in order the get the build working as index structures changed due to the removal of the ttl attribute.

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cbbb293 should be back ported to `1.5.x` - some minor glitches there but doable.