* Moved attachaments POST url from /issues/attachments to /attachments
* Implemented attachment upload on release page
* Implemented downloading attachments on the release page
* Added zip and gzip files to default allowed attachments
* Implemented uploading attachments on edit release
* Renamed UploadIssueAttachment to UploadAttachment
* Implemented sendmail. This piggybacks on existing configuration to keep the change simple
* Changed privicy of new sendSMTP and sendSendmail functions
* Fixed Lint errors
* Seperated SMTP and sendmail into their own senders
* Making new structs private as they should not be used externally now
* Added sendmail setting to ini file
* Minor code cleanup