Add Versions

* Add the `versions` command to list all of a Project's Versions
  in a table format.
* Add the `version` and `nextversion` command to list the details of a
  specific Version and the next Version that is due for a Project.
* Add the Version and Versions types to represent Redmine's Versions.
* Add the getProjectsIssues and getVersionsIssues functions to retrieve
  specific sets of Issues.
* Add the getVersion, getVersions and getNextVersonDue functions to
  retrieve Versions and lists of Versions.
* Add the versionDetail function to render the details of a single
  Version.
* Add the versionTable function to render Versions into a Table.
* Add the getProjectFromIdent to retrieve a Project from it's Identifier
  or the string representation of its Id.
* Add the ProjectIdent and VersionId types to better docuemnt type
  signatures.
* Add the IssueFilter type to represent filtering options on Issue GET
  requests.

* Modify the getAllIssues function to actually query for all issues
  instead of a single Project's.
* Split the commands in the usage text into sections.

* Remove the Projects, Statuses and Issues types from Redmine's public
  API.

* Fix a bug causing invalid GET queries.