Implement TCR review suggestions (#221)

* feat(t2cr): include symbolMultihash in submission event

* docs(t2cr): fix typo an clarify docs

* fix(t2cr): calculate amount required for side locally

This removes jumping to the old calculateRequiredFor side function.

* feat(t2cr): allow any account to withdrawl from contract

* docs(t2cr): clarify comment

* refactor(t2cr): fix function ordering

* fix(t2cr): remove arbitrator data struct

The struct is no longer needed since there are no functions exceeding stack limit.

* docs(t2cr): clarify docs and fix typos

* fix(t2cr): remove unused code and refactor

* feat(t2cr): allow withdrawing rewards from request in batches

* feat(t2cr): allow updating meta evidence

:skp