Keep web app meta and dirs in separate classes

WebApp class has contained both WebAppMeta and dirs fields.
Dirs have been moved to a new class WebAppStorage and
WebApp class has been removed.

Signed-off-by: Jiří Janoušek <janousek.jiri@gmail.com>
Use real web app icon in a desktop file

Signed-off-by: Jiří Janoušek <janousek.jiri@gmail.com>
Add utility functions for camel and dashed id

build_camel_id() creates CamelCase web app id,
build_dashed_id() creates id with dash-separated
words

Signed-off-by: Jiří Janoušek <janousek.jiri@gmail.com>