Revert "Implemented fs2mod format and added various improvements."

Moved development to the develop branch.
Merge branch 'develop'
Merge branch 'develop'
Release 0.1.0.dev3
* Improved the build system
* Refactored repo storage (mods are now stored in ~/.knossos/mods.json)
* Fix issues on Linux where FSO depends on missing libraries
* Added the "executable" property to packages
* Added a new condition type to packages: "bool"
* Added code to make the converter download files from box.com
* Added (experimental) version pinning for mods.
* Fixed a few minor bugs.