Refactor commands library

[wyozi]

• Parsing arguments should use a promise; eg paths can't be validated without them
• Avoid using register command and a million callback_ prefix functions
• IPC should be first class aka not implemented using hooks but core code
• Arguments should map directly into a netmsg schema for transparent optimization
• Avoid ambiguous argument flags, such as take_rest (sometimes it needs to be used for more parameters than just the last one)
• Should server and clientside functions go through different validation pipeline (clientside input needs to be always validated, but should serverside input be validated as rigurously?)
• IPC should not be a string parameter. Netmsg id/name should automatically be derived from command id
• Clear distinction between server and client commands! Should it even be possible for clients to be purely clientside?
• Testability! It should be possible to test each part of IPC pipeline independently