Add db management system libraries for rest of the databases

[cyanogus]

This was added for the currency system's database. Since no problems were reported from use after it's implementation, I feel like it's time to implement this change to the other databases as well.

[cyanogus]

So far I've worked on the levelling db part of it. I'm currently working on the items db part and the other ones are yet to be completed.

[cyanogus]

Added database library support for weather cog.

[cyanogus]

Alternative pull request was made for Weather DB commands. #310
Another alternative pull request was also made for Levelling DB commands. #307

[notsniped]

This PR contains the following topics which need to be replicated in other PRs:

• Items
• Levels
• Weather

[notsniped]

Am currently working on items db support.

[notsniped]

Functions that need to be added for items db

• load() - Loads the database into a variable
• save() - Dumps the variable data into local machine db
• generate() - Generates a new key for the user (and adds any missing item values), but skips if user already exists
• add_item() - Adds an item of a specified quantity
• remove_item() - Removes an item of a specified quantity
• fetch_item_count() - Returns the number of a specified item a user has in their inventory

[notsniped]

A new pull request for base implementation of items db has been made.
#312

[notsniped]

Now, for the items db, full migration of commands using items, and testing will be done.

[notsniped]

A complete version of items db was made at #313

[notsniped]

The PRs mentioned above have covered all of the changes of this one PR. This PR will now be closed. Thank you for your time!

[notsniped]

PRs: #307 #310 #312 #313