EESSI bot v0.7.0

This is a minor release of the EESSI build-and-deploy bot.

Bug fixes:

• bot only reports moving to trash_bin when relevant (#292)

Improvements:

• add support for specifying that build job script is located in another repository (#283)
• implement exportvariable filter (#288, #291)
  • see related configuration setting allowed_exportvars
• add alternative method to submit job (using --begin=now+SOME_DELAY) (#297)
  • also see the new related configuration settings job_handover_protocol and job_delay_begin_factor
• set the local_tmp that is configured for a site as tmpdir in bot build job script (#299)
• add setting for a script to customize build environment (#302)
• add support for signing tarball and metadata file and uploading signatures to S3 bucket (#303)
• add SSH signing script sign_verify_file_ssh.sh (#304)
• updates of the docs (#293, #298)

Changes to app.cfg settings (see README.md and app.cfg.example for details):

• NEW (optional) allowed_exportvars in section [buildenv]
• NEW (required) awaits_release_hold_release_msg in section [submitted_job_comments]
• NEW (required) awaits_release_hold_release_msg in section [submitted_job_comments]
• DEPRECATED (optional) awaits_release in section [submitted_job_comments]
• NEW (optional) job_delay_begin_factor in section [buildenv]
• NEW (required) job_handover_protocol in section [buildenv]
• NEW (optional) signing in section [deploycfg]
• NEW (optional) site_config_script in section [buildenv]