Added base Web App functionalities and models. Minor fixes.

.../base_app/static/icons/mimetypes/application-x-python.png

...tta/base_app/static/icons/mimetypes/application-x-rar.png

...tta/base_app/static/icons/mimetypes/application-x-rpm.png

...ta/base_app/static/icons/mimetypes/application-x-ruby.png

..._app/static/icons/mimetypes/application-x-shellscript.png

...tta/base_app/static/icons/mimetypes/application-x-tar.png

...ta/base_app/static/icons/mimetypes/application-x-tarz.png

...tta/base_app/static/icons/mimetypes/application-x-xar.png

...tatic/icons/mimetypes/application-x-xz-compressed-tar.png

...etta/base_app/static/icons/mimetypes/application-x-xz.png

...tta/base_app/static/icons/mimetypes/application-x-zip.png

...tta/base_app/static/icons/mimetypes/application-x-zoo.png

...setta/base_app/static/icons/mimetypes/application-zip.png

...pp/code/rosetta/base_app/static/icons/mimetypes/ascii.png

...de/rosetta/base_app/static/icons/mimetypes/audio-mpeg.png

...rosetta/base_app/static/icons/mimetypes/audio-x-adpcm.png

.../rosetta/base_app/static/icons/mimetypes/audio-x-aiff.png

...etta/base_app/static/icons/mimetypes/audio-x-flac+ogg.png

.../rosetta/base_app/static/icons/mimetypes/audio-x-flac.png

...setta/base_app/static/icons/mimetypes/audio-x-generic.png