Make sure dbListTable and other functions that use as_of can handle timestamps

[n8layman]

Some of the functions that use as_of can accept a timestamp instead of a commit hash in order to go utilize older versions. Make sure that that feature:

• works with all as_of aware functions
• Can identify the proper commit hash given a timestamp
• works with functions that use the qualified hash method. I.e. dbName/<commit hash>.tableName
• Also make sure all as_of functions can also accept aliases like 'HEAD' or 'HEAD~2'