Various fixes to project handling and docs

[zatherz]

This is a merge of #47, #46 and #45. If you're going to merge these, please merge this PR instead, as #46 and #47 contain merge conflicts which this PR has solved.

• Properly interpret double slashes in documentation

• Fix build paths Build commands which are supposed to run with the whole project will now start at the root of the current open directory in Sublime, which allows you to put your source files e.g. in a source sub directory and still have Build with: dub compile the project.

• Improved 'Update Import Paths', various other fixes

  • Update Import Paths now also runs Update Project first
  • Restart DCD Autocompletion Server now actually restarts the server - tries to kill it first.
  • Added the port number to some things that lacked it, like the 'Restart DCD Autocompletion Server' check for whether the server is already running (and that check can be overriden using the new 'force' argument)
  • New 'Kill DCD Autocomplete Server' command to shut down dcd-server

[yazd]

Thank you for the contribution. I'll review this the soonest.