Bbtag update phase2

[danny-may]

Most of this update revolves around the update to the engine. While not perfect or anything, this new one does allow for greater control over scopes and what gets passed around between subtags during execution.

Backend Changes

1. Added BBTagEngine.js - All the complex stuff goes here. Includes all the logic for processing and responding to tag execution requests
2. Various updates to match this new engine - The bulk of the changes to all subtags have been as follows:

• params.args => args (now 0 indexed rather than 1 indexed)
• whenArgs(x => whenArgs(x-1
• beforeExecute(.... => removed. Subtags which previously had no before execute now have resolveArgs which you supply with arg indexes to resolve.
• params.msg => context.msg
• params.channel => context.channel
• params.channel.guild => context.guild
• params.msg.author => context.user
• params.msg.member => context.member

3. Variable caching - Now all variables will be cached in-memory upon first access/set and wont be persisted to the database until the tag completes. This 1. provides better protection against malformed data in the event of an internal server error, 2. speeds up all variable types to nearly the same speed as temporary variables and 3. enables operations that may have been previously too costly to be added in the future.

"Front" end changes - The stuff users gon see

1. Added b!cc test <code>, b!cc test debug <code>, b!cc debug <CCName> [args...], b!t test debug <code> and b!t debug <tag> [args...]. Debug statements will cause an attachment to be sent which will contain all the useful information about the tag execution. While not comprehensive, it does have better error tracking and a dump of the final variable values.
2. Removed the silly restriction on the docs for cc only subtags. Idk why I thought this was a good idea, sorry support :notlikecat:
3. Better {exec[cc]} - Now rather than it being a limit of 200 calls per tag, its instead a maximum depth of 200 calls. I intend to do something similar for the loop tags (for, foreach and repeat) but I need to figure out how to approach that first.

Bug fixes
Ive done various fixes on my way through this PR, the notable ones I can think of off the top of my head are:

1. Fixed a logical error in slice causing internal server errors
2. Fixed rolemes being completely mute
3. Fixed cats typos on {userbot}
4. Fixed an error or two on edit when the message is not found
5. Finally fixed a dumb persistent issue with capitalize
6. Fixed a shard kill that {inject} could cause

Next phase
This update, because its actually less breaking than the previous one, has been kept rather feature light. This is because I am intending to add a lot of new subtags for the next big PR I do:
{listreact}
{removereact}
{waitreact}
{waitmessage}
{function} (creates a function)
{call} (calls a function)
{getmessage}
{hasperm}
{userexists}
{rolemove} and a few other tweaks and features