Remove the site_data JSON file

This is no longer being used because of the limitations GitHub places on
requests for files from repos.
Split E2E tests into 'Integration' and 'System'

Separating out the tests helps to flatten the directory structure a bit and
remove some of the cruft. Also replaces ill-defined custom name for a part of
the testsuite with the standard automated testing names.
Includes several similar flattening fix to the tests.utils package, moving
tests.utils.exceptions into tests.utils
Move unit test files into tests/testfiles

The testfiles are supposed to be shared files for all tests to operate upon.
Moved files into there and made shared functions to operate on them. Includes
renaming from numerical names like 'valid1.txt' to semantic ones like
'empty_file.txt' Some of the manifest naming is a little lazy, but minimally
correct. Config testing does not need a subdir, since it is just a module, not a
package, so config_test has been moved into tests/unit
Rename AbstractBlock to Block; Block to CoreBlock

This renaming makes the API package much clearer, since the highest level block
abstraction is unqualified, and specializations of it are given qualifiers.
Convert salve.util into a set of salve.* modules

There is still a 'util' module, contianing miscellany from the util package
like Enums, but context, exception, and log handling has been moved into the
higher level namespace for simpler, more direct access. As a slight naming
change, instead of salve.error, there is 'salve.exception'
Renamed tests.util.file_path to full_path

This is a more accurate name, since file_path can be used on directories.
Merge branch 'refactor/2-3-0-cleanup' into dev