feat: change naming convention between metadata and storage

metadata now stores both blockid and storageid.

The block is now referred in the metadata as blockid (as before)
The block is referred via its storageid in block storage. i.e The block
is stored by the name of storageid

The storage id is generated using a uuid5, which uses a default namespace of
uuid.NAMESPACE_DNS and blockid as the name.
pep8: pep8 fix, and remove unused import
Merge remote-tracking branch 'upstream/master' into meta_storage_name_change
Update assign blocks operation
Fix status code check for Blocks HEAD
fix: storage id's uuid5 generation using both timestamp and blockid

- Cassandra and Mongo now natively store uuid5, Sqlite doesnt have
  support for it, so its going to be text there.

- Updates all the metadata and storage drivers to make use of the change

- storage_id method is now part of the BlockStorageDriver Abstract Base
  Class
Merge remote-tracking branch 'upstream/master' into meta_storage_name_change
Assign a block to a finalized file
fix: head block

_storage_has_block now checks for a block in storage
using the storageid instead of the block id.
update: Readme.md

Remove a line in the instructions that asked to copy over the
configspec.ini file.

This is no longer required, since irrepective of the location of the
config.ini file (in supported locations). It is always validated and
transformed against configspec.ini within the repository.
fix: 412 and 413 status codes to 409 - HTTP CONFLICT
fix: don't always load default config

This patch resolves a bug whereby we were always loading the default
config if other configs existed.
Merge pull request #179 from painterjd/fix_config_using_local

fix: don't always load default config
Merge remote-tracking branch 'upstream/master' into status_code_fix
Merge pull request #175 from jc7998/fix_test

API Test: Fix status code validation for Block HEAD
Merge pull request #174 from jc7998/assign_blocks

API Tests: Update assign blocks operation with new schema
fix: move UUID conversion to metadata drivers

Now, the get_storage_id function generates uuid5s' and returns them
after casting to str.

The individual metadata drivers themselves transform it to UUID format.
feat: allow query of blockid using storage id in metadata

Notes:
- Cassandra: added an index on storageid.
  For eg: It would allow queries to use storage id in the 'where'
  clause while using CQL
fix: add hostname to uuid5 generation
fix: change storage_id to be a static method