JavaDoc fixes & enhancements RocksJava

This pull request does not include any code changes expect commentary documentation.

List of Changes:
- JavaDoc readability of RocksObject JavaDoc
- JavaDoc improvements BlockBasedTableConfig, GenericRateLimiterConfig, RocksDB
- JavaDoc improvements MemTableConfig
- JavaDoc improvements RocksObject
- JavaDoc improvements GenericRateLimiterConfig
- JavaDoc improvements ReadOptions
- JavaDoc improvements RateLimiterConfig
- JavaDoc improvements RestoreOptions
- JavaDoc improvements RestoreBackupableDB
- JavaDoc improvements BlockBasedTableConfig
- JavaDoc improvements Options
- JavaDoc improvements BackupableDB and BackupableDBOptions

After applying that changes JavaDoc will not generate any warnings or error messages.
Verify with:

```
cd java
javadoc -sourcepath ./ -protected -use -splitindex -nodeprecatedlist -d ./doc -subpackages org.rocksdb
```