Move helm/anything plugin to corresponding directory

This commit is for convenience of making MELPA recipe.


I plan to divide `prosject` into three following packages for MELPA. Because all users don't need helm or anything.

1. `prosject` which include:

    prosjekt.el
    prosjekt/ext/async-shell-command-prosjekt.el
    prosjekt/ext/dirtree-prosjekt.el
    prosjekt/ext/find-project-file-prosjekt.el

2. `anything-prosjekt` which include:

    anything-prosjekt.el

3. `helm-prosjekt` which include:

    helm-prosjekt.el

To do this, separated directories for plugins is convenient for making MELPA recipe. Currently, MELPA recipe format can't exclude files. See https://github.com/milkypostman/melpa#recipe-format. Then MELPA recipes for three packages in the present directory structure is as follows:

1. `prosject`

        (prosjekt :fetcher github :repo "abingham/prosjekt"
                  :files ("prosjekt/*.el"
                          "prosjekt/ext/async-shell-command-prosjekt.el"
                          "prosjekt/ext/dirtree-prosjekt.el"
                          "prosjekt/ext/find-project-file-prosjekt.el"))

2. `anything-prosjekt`

        (anything-prosjekt :fetcher github :repo "abingham/prosjekt"
                           :files ("prosjekt/ext/anything-prosjekt.el"))

3. `helm-prosjekt`

        (helm-prosjekt :fetcher github :repo "abingham/prosjekt"
                       :files ("prosjekt/ext/helm-prosjekt.el"))

If you will want to adding elisp file to `ext` directory in future, you need to update `:file` to add the elisp file.

If This commit is merged, MELPA recipes for three packages is as follows:

1. `prosject`

        (prosjekt :fetcher github :repo "abingham/prosjekt"
                  :files ("prosjekt/*.el" "prosjekt/ext/*.el"))

2. `anything-prosjekt`

        (anything-prosjekt :fetcher github :repo "abingham/prosjekt"
                           :files ("prosjekt/ext/anything/anything-prosjekt.el"))

3. `helm-prosjekt`

        (helm-prosjekt :fetcher github :repo "abingham/prosjekt"
                        :files ("prosjekt/ext/helm/helm-prosjekt.el"))

You can add elisp file to `ext` directory without updaging MELPA `prosject` recipe.