Add MySQLi Database Driver + MySQLi SSL support

[enov]

Adding MySQLi Database Driver and MySQLi SSL support by cherry-picking related commits that has been merged to 3.4/develop branch.

[enov]

Related to #91

[rjd22]

@enov normally this would not be allowed because it is a big change. But since you are only adding API and not changing it I am prepared to give a 👍

@zombor and @shadowhand would this be acceptable?

[enov]

I understand @rjd22. I'll just leave it here for someone else to merge.

[acoulton]

Can we add this as a commented out example rather than adding a new alternate_ config group?

• We don't want to encourage end-users to actually use the alternate_ connection to extend our default config
• In the unlikely case a user already has an alternate_ db, we don't want to pollute that config

I know that's different to how the other groups appear, but it is consistent with what we ended up doing in kohana/cache so that the module just ships with example config but it's for end users to copy/paste/configure
their own connections however they want them.

[acoulton]

I'd be +1 in adding this to 3.3, if the additional config block gets commented out.

[enov]

The additional config block is commented out now. Thanks.

[acoulton]

@enov grand, I think given you, me and @rjd22 are +1 we should just go for it - so I've merged.

[enov]

Thanks @acoulton 😄 !