Added base Web App functionalities and models. Minor fixes.

...ta/base_app/static/icons/mimetypes/application-msword.png

...e_app/static/icons/mimetypes/application-octet-stream.png

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

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

...ons/mimetypes/application-vnd.android.package-archive.png

...icons/mimetypes/application-vnd.debian.binary-package.png

...app/static/icons/mimetypes/application-vnd.iccprofile.png

...e_app/static/icons/mimetypes/application-vnd.ms-excel.png

...etypes/application-vnd.ms-excel.sheet.macroEnabled.12.png

.../static/icons/mimetypes/application-vnd.ms-powerpoint.png

...cation-vnd.ms-powerpoint.presentation.macroEnabled.12.png

...ypes/application-vnd.ms-word.document.macroEnabled.12.png

...xmlformats-officedocument.presentationml.presentation.png

...vnd.openxmlformats-officedocument.spreadsheetml.sheet.png

...enxmlformats-officedocument.wordprocessingml.document.png

...p/static/icons/mimetypes/application-vnd.rn-realmedia.png

...pp/static/icons/mimetypes/application-x-7z-compressed.png

...ta/base_app/static/icons/mimetypes/application-x-7zip.png

...a/base_app/static/icons/mimetypes/application-x-addon.png

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