Remove collection_info license spdx validation

[alikins]

SUMMARY

Remove collection_info license spdx validation

Remove loading, parsing, and checking of spdx_licenses.json
on every CollectionInfo() creation.

Allow mazer to read/write collections with licenses that
are not one of the SPDX licenses, including the default
'all rights reserved'

Fixes #168

An alternative to #169

ISSUE TYPE

• Bugfix Pull Request

MAZER VERSION

name = mazer
version = 0.3.0
config_file = /home/adrian/.ansible/mazer.yml
uname = Linux, newswoop, 4.18.12-100.fc27.x86_64, #1 SMP Thu Oct 4 16:22:17 UTC 2018, x86_64
executable_location = /home/adrian/venvs/galaxy-cli-py3-2/bin/mazer
python_version = 3.6.6 (default, Jul 19 2018, 16:29:00) [GCC 7.3.1 20180303 (Red Hat 7.3.1-5)]
python_executable = /home/adrian/venvs/galaxy-cli-py3-2/bin/python

ADDITIONAL INFORMATION