hashdist.cli.manage_store_cli: PEP 257 docstring for InitHome

Use a phrase ending with a period [1], followed by a blank line and
additional details [2].  This avoids 'hit --help' output like:

    init-home           Initializes the current user's home directory for
                        Hashdist by
    mv                  Moves a ...

I also switched to the canonical 'HashDist' capitalization.

[1]: http://legacy.python.org/dev/peps/pep-0257/#one-line-docstrings
[2]: http://legacy.python.org/dev/peps/pep-0257/#multi-line-docstrings
hashdist.cli.frontent_cli: PEP 257 docstring for BuildDir

Use a phrase ending with a period [1].  I also broke off a trailing
phrase to stay under 80 characters [2].

[1]: http://legacy.python.org/dev/peps/pep-0257/#one-line-docstrings
[2]: http://legacy.python.org/dev/peps/pep-0008/#maximum-line-length
hashdist.cli.frontend_cli: PEP 257 docstring for Build

Use a phrase ending with a period [1], followed by a blank line and
additional details [2].  This avoids 'hit --help' output like:

    build               Builds a profile in the Hashdist YAML profile spec
                        format, and
    build-postprocess   Walks through ...

I also switched to the canonical 'HashDist' capitalization.

[1]: http://legacy.python.org/dev/peps/pep-0257/#one-line-docstrings
[2]: http://legacy.python.org/dev/peps/pep-0257/#multi-line-docstrings
hashdist.cli.build_tools_cli: PEP 257 docstring for BuildPostprocess

Use a phrase ending with a period [1], followed by a blank line and
additional details [2].  This avoids 'hit --help' output like:

    build-postprocess   Walks through directories to perform the actions given
                        by flags
    build-unpack-sources
                        Extracts ...

which cut off in mid-sentence.  Now it cuts off in the same place, but
it's clear on the docstring side that it's the end of the sentence ;).

I also switched to imperitive 'Walk' instead of the implicit
description '[This command] Walks' [1].

[1]: http://legacy.python.org/dev/peps/pep-0257/#one-line-docstrings
[2]: http://legacy.python.org/dev/peps/pep-0257/#multi-line-docstrings
hashdist.cli.build_tools_cli: PEP 257 docstring for BuildUnpackSources

Use a phrase ending with a period [1], and switch to imperitive
'Extracts' instead of the implicit description '[This command]
Extracts' [1].

[1]: http://legacy.python.org/dev/peps/pep-0257/#one-line-docstrings
Merge pull request #266 from wking/pep-257-docstrings

PEP 257 docstrings for command-line commands