Delete enhancement

[Flamefire]

Fixes #50

You can now delete releases based on type (all, draft, prerelease or release) and on age (-older-than HOURS)

Also updates the docu (was missing verbose and dry-run) and fixes a performance bug: Releases were loaded in delete and again before deleting a single release causing a unnecessary slow down

[Flamefire]

@jcfr The failures are due to the missing token. Anything I could do to make it pass? Otherwise can this be merged?

[jcfr]

For future reference, the integration of this PR has been voided by force pushing master to integrate the following branches:

• created branch `support-delete-given-release-type' with two commits:
  • https://github.com/j0057/github-release/commit/7e73cf9e780e38e010eff533a4bc1158b6f0f8e5: gh_release: Speed-up release deletion
  • https://github.com/j0057/github-release/commit/fc7e693177f17bef281fd45a1b678ae36d5f62dd gh_release: Support deleting releases based on release type
• created branch support-delete-based-on-age with one commit:
  • https://github.com/j0057/github-release/commit/ea6b00d754fc818411bd81382c3ac44dbb4a3dbe Add older-than switch to limit deletion by age

Finally, the CHANGES document has also been updated to reference the feature addition and performance improvement.

@Flamefire Thanks again for your patience and for your contributions :pray: