Uniform insert operations in follow and reblog

Feed cache changes:

• Redefined primary key in FeedCache
• Added block_num column to FeedCache
• FeedCache is now build during initial sync
• Batch insert added to FeedCache following batch insert scheme from other classes

Other changes:

• Added setup_shared_db_access method to class DbAdapterHolder, after initial sync all classes basing on this class will use single db connection to use transaction properly in listen method
• Insert operations in follow and reblog are uniform accross sync mode (initial and live sync)
• Above fixes crash when initial sync is followed by live sync
• Added current system time to logs