Orca 679 global atlantis lock

[msarvar]

Added support to create a command specific lock entries to the db/bolt_db, LockCommand, UnlockCommand, and CheckCommandLock.

Implemented a new ApplyLocker interface for locking.go#Client that manages apply lock creation/deletion and lock retrieval.

LocksController has 2 handlers to create and delete apply locks.
Server#Index renders the UI to create/delete the locks.
ApplyCommandRunner expects an object that implements ApplyCommandLocker which boils down to object having IsDisabled function that returns boolean value.
DefaultApplyCommandLocker implements the interface.

In UI it is just a AJAX request that will create/delete the locks for apply. To create a new lock or delete existing one do to atlantis main page.

[msarvar]

/ptal @nishkrishnan

[msarvar]

/ptal

[nishkrishnan]

I actually think it makes sense to rebase your change on on top of our new release branch to make the review easier to know what we've added and what exists in the branch already.